refactor: replace deprecated String.prototype.substr()

.substr() is deprecated so we replace it with .slice() which works similarily but isn't deprecated
Signed-off-by: Tobias Speicher <rootcommander@gmail.com>

2.2.4

Changes for 2.1.54

- Fixed Diagram.viewSize when setting it to a real value and then later setting it back to a NaN value.
- As with 2.1.52, fixed more scenarios with custom animations improperly adding state to the AnimationManager.defaultAnimation.
- Fixed rare cases of LayeredDigraphLayout trying to get the "centerX" property of a null vertex.

- Fixed Binding.ofModel binding when there is no Diagram and thus no Model to just ignore the binding.
- Fixed a regression in Diagram.makeSVG from 2.1.49 when using a Panel.Spot with Panel.isClipping set to true, where some elements would get grouped and positioned incorrectly.
- Fixed Model.toJSON output when object keys contained unescaped double-quote characters.
- Fixed some Shape Geometry intersections (such as with Link connections) when the Shape's Geometry contained small and flat beziers.
- Fixed collapsed Parts incorrectly causing their Groups to remeasure, which may have caused Group's connected Links to re-route.

Changes for 2.1.52

- Fixed animations incorrectly resetting some link routes.
- Fixed custom animations improperly adding state to the AnimationManager.defaultAnimation.
- Fixed a regression in 2.1.51 where un-modeled parts containing Images, that are added before a model is set, may fail to load.
- Fixed a regression from 2.1.50 when Picture.errorFunction was used to modify the Picture.source or Picture.element, which would cause a "Collection was modified during iteration" error.

- The TextEditingTool, when the user has entered an invalid text string, has always called any TextBlock.errorFunction and then continued showing the text editor so that the user could fix their text entry. The TextEditingTool.doError method now calls any TextBlock.errorFunction and also calls HTMLInfo.show on the TextEditingTool.currentTextEditor. This will allow an override of TextEditingTool.doError not to continue showing the editor. If you have not overridden that method, which was new in 2.1, this change will not affect you.
- Fixed Model.fromJson not to substitute instances of classes such as Point and Size when the Object's "class" property had a value that is "Point" or "Size". The property value must be what is produced by Model.toJson, which uses values such as "go.Point" or "go.Size". The documentation lists all of the substitution cases that Model.fromJson handles.
- Fixed a regression from 2.1.43 which caused some links to animate routes incorrectly upon dragging.
- Fixed loading Images used as a Picture.element.
- Improved some AvoidsNodes routing of Links when connecting Nodes in different Groups and the Groups are not Group.avoidable.
- Fixed using multiple license keys.

Changes for 2.1.50

- Enhanced the LinkShiftingTool extension to support links that are only connected at one end.
- Fixed CommandHandler.doKeyDown to support Robot.keyDown use of "F2" and "ContextMenu" keys.
- Improved routing of AvoidsNodes links that have a "to" end segment with a direction that is a multiple of 45 (but not 90) degrees.
- Fixed diagram not redrawing after images load in frameworks that use a shadow DOM, such as Angular.
- If you call TextBlock.setBaseline or TextBlock.setUnderline outside of your diagram initialization, you should also call Diagram.redraw on all Diagrams.

- Added the Flow PanelLayout extension, demonstrated in the Flow PanelLayout sample. This panel layout (not a diagram layout!) arranges panel elements into rows or columns. As time goes by we may add more properties to control the behavior of this custom panel layout.
- Fixed undo/redo bug involving setting RowColumnDefinition properties and calls to Panel.removeColumnDefinition.
- Fixed Picture.successFunction erroneously being called twice in some situations, such as when a node was copy-pasted.
- Fixed Diagram.makeSVG not rendering shadows on some GraphObjects.
- Fixed Diagram.makeSVG not clipping when using a Panel.Spot with Panel.isClipping set to true.
- Improved visual consistency of shadows in SVG output from Diagram.makeSVG

- Fixed Panel.removeRowDefinition and Panel.removeColumnDefinition to decrease the Panel.rowCount and Panel.columnCount when the highest index RowColumnDefinition is removed.
- Fixed Picture.successFunction, which was called for only the first Picture with a given unique Picture.source. It is now called for every Picture that has a successFunction defined with the same (successfully loaded) source.

- Fixed Diagram.layoutDiagram not performing a layout immediately if called within an ongoing Diagram update (such as during a DiagramEvent like "InitialLayoutCompleted").
- Fixed Panel.itemTemplate so that it is used, not the default item template, when the panel cannot find any template with the given category name in the item data.
- Diagram.viewSize, if set, now takes precedence over the size of the Diagram.div. It is not typical to set both a DIV and the viewSize, but in environments where a DIV is set automatically it may be useful for testing purposes to set an explicit viewSize as well.

- Fixed an issue with indefinite animations causing some transactions to skip the UndoManager.
- Fixed Diagram.makeImageData to draw any other Parts in the "Grid" Layer besides the Part holding the Diagram.grid when the showGrid option is true but the showTemporary option is false.

- Fixed a bounds calculation bug with PathSegment.SvgArcs, when the arc has a zero X or Y radius value.
- Link route calculations now avoid an effectively infinite loop due to floating point errors when the two ports almost exactly overlap each other.
- Fixed an occasional exception when dragging a disconnected link when the link had no points in its route.
- The GraphObject.naturalBounds of a Shape now always prefers GraphObject.desiredSize if it exists, over the Shape's Geometry.bounds. These are usually the same, but a Geometry with beziers can be slightly off from the desiredSize used to create it.

-  Fixed a regression from 2.1.28 with some Shape.geometryString paths. If a path contained an arc command that was closed, a relative move command afterwards would be at the wrong coordinates.

- Improved performance of LayeredDigraphLayout for large graphs when LayeredDigraphLayout.packOption is set to LayeredDigraphLayout.PackAll. Setting LayeredDigraphLayout.packOption to a subset of the possible flags has always helped performance at the expense of improved layout. Also, it has always helped to set LayeredDigraphLayout.aggressiveOption to LayeredDigraphLayout.AggressiveNone.
- Fixed non-default indefinite animations preventing the default animation from starting. Fixed some other non-default animation bugs, such as indefinite animations preventing Overviews from updating.
- Enhanced LinkingTool.findLinkablePort, when LinkingTool.startObject is a Node and the whole node is not a port, to return the node's default port Node.port instead of null, if the port is a valid port for linking from or to.

- Fixed an animation bug with ResizingTool where it would disable all animations on resizing.
- Setting AnimationManager.isEnabled to false and then true again will resume any indefinite animations (animations with Animation.runCount set to Infinity).
- Fixed a bug in RadialLayout where it wasn't properly resetting its network. This was most often seen when using with Diagram.delayInitialization (including gojs-react and gojs-angular).

- Improved the animation of colors in Animations.
- Added the Spot Rotating Tool extension, demonstrated in the Spot Rotating sample. This is basically the RotatingTool extended to support an additional Adornment and handle for letting the user interactively move the RotatingTool.rotationPoint by setting Part.rotationSpot.
- Added an Introduction page about Using GoJS on Different Platforms, summarizing existing resources for them.