dom

When looking up an attribute with .attr(), the name of the attribute should be lowercased before looking up in .attribs object.

Relevant spec sections:

https://drafts.csswg.org/selectors-4/#the-dir-pseudo
https://html.spec.whatwg.org/multipage/semantics-other.html#selector-ltr

The interesting cases to test are from the definition of "directionality" in HTML:
https://html.spec.whatwg.org/multipage/dom.html#the-directionality

• element with dir="ltr" matches :dir(ltr) (#26159)
• root element without `

Describe the feature you'd like:

As far as I understand it, the toHaveDisplayValue matcher takes some kind of input element and computes the value that the user can see.
However, it does not work properly for range widgets (e.g. <input type="range">, but also elements with role="range" or role="slider").

According to the [standard](https://www.w3.org/TR/wai-aria-1.1/#aria-valu

Recently @devrnt opened up a PR to improve the setup with a theme(#189) and I realised that it'll be awesome to have that section expanded for each case.