flight-simulation

JSBSim provides schemas for XML validation (JSBSim.xsd for flight models, JSBSimScript.xsd for script files and JSBSimSystem.xsd for system files) but they have not been updated for a while so they might reject perfectly valid XML files.

XML files can be tested with xmllint

> xmllint --noout --schema JSBSim.xsd some_path/my_file.xml

It might be interesting to:

• Upd

Add cm, dm aliases for descend/climb, tr, tl for t l/t r.

These commands are common in VATSIM trainer software, such as TWRTrainer and ESKey for EuroScope.

Add the option to have a notification sound for any text message, and one for any text message on UNICOM.

We should document these new dataclasses and the new enum. The docs in the code would be fine to copy & paste into the README, with the appropriate formatting.

Seasonalisation? Is that even a word?

Anyway, seasonal support can be improved, particularly snowy winter, by producing new versions of textures with snow incorporated, e.g. snowy roofs.

Unfortunately for the vast majority of the library we can't use the same approach as [Winterizer](https://forums.x-plane.org/index.php?/files/file/51354-winterizer-a-tool-for-snowy-orthophotos/&tab=comments&