* Add disabled state example to the .form-control page

* Document disabled attribute on select too

* Add disabled example for file input

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

Edge Legacy support filling their track by default.

Example: https://codepen.io/coliff/pen/VwaZgVZ

* Expand on disabled fieldsets and faked buttons

include further advice/information on how to disable faked buttons for keyboard/AT users

* Centralise accessible name advice in forms overview

seems odd to only mention (separately) label, aria-label etc in input-group and layout. the advice is just as pertinent in other sections like select. checks only skims over this.

moving this, in expanded form, into the overview section itself. adding a specific cross-reference (just because they are easily left with no accname at all) in the checks page.

* Change warning about accessibility, modify server-side example

- paradoxically, due to our current problems with validation (see #28414

) and the fact that browsers seem to have improved in this area for the most part, it's now actually better to use browser-native validation
- added explicit `id` and `aria-describedby` association to at least the server-side form error messages, to show how it should be done properly, and expanded the prose for that explaining this.

* Replace `.sr-only` with `.visually-hidden` in new addition

* Copy edits for clarity in parenthetical

* Copy and formatting tweaks

- Wordsmithing here and there
- Turns some hyphens into em dashes
- Turns a long running comma separated list into an unordered list
- Rearranges some copy just a bit

Co-authored-by: Mark Otto <markd.otto@gmail.com>

"screen readers" is quite reductive, as there are other assistive technologies. content hidden this way is even announced by things like Alexa/Siri etc, so it's not so much just "screen readers".
in the long run, we may even consider changing the actual classnames (maybe `.visually-hidden` / `.visually-hidden-focusable`, though admittedly that's a bit verbose).

also includes a tiny tweak to layout.md to generalise the note about using `.sr-only`

* Keep checks/radio toggle buttons on topic

- give examples of the pure toggle checks and radios, without the button group class. show that these work fine without `.btn-group`, but still cross-reference it
- move the explanation from "Checkbox toggle buttons" directly to "Toggle buttons", as the mention of using button classes applies equally to the subsequent "Radio toggle buttons" and "Outlined styles" subsections.

* Expand button group description

as it's not just single line, but vertical as well

* Expand button group examples

- add more colour ... `.btn-secondary` is just dull and uninspiring
- new section to showcase "Checkbox and radio button groups"
- add a mixed styles example
- add an example of vertical radio button group

* Rename `sr-only`/`sr-only-focusable`

To be more representative of the fact that these are not necessarily "screen reader" specific, but actually apply to assistive technologies in general (and also things like Alexa/Siri/etc). Goes hand-in-hand with #31133

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

* Docs: improve/expand button documentation

- since we're not doing the disabled cursor thing anymore anyway, remove confusing/unnecessary mention for link-based disabled buttons
- make the disabled toggle example using a link actually follow the preceding advice of also having `tabindex="-1"` and `aria-disabled="true"`
- tweak the link functionality callout to also still mention `aria-disabled` to reinforce the idea
- tweak toggle state description (not just `<button>`s, but also links etc...so just remove mention of `<button>` there; also reinforce accessibility aspect once more)
- add a new callout that cross-references checkbox-based toggles, and what the similarity/difference between them is
- add a matching cross-reference callout to the checkbox-based toggle buttons page

* Update link to now renamed checks-radios.md

* Docs: rename form checks page to "Checks / radios"

it's not immediately obvious that "checks" includes information about both checkboxes and radio buttons. while "checks / radios" is also still not perfect (as honestly even I didn't quite grok that "checks" meant checkboxes), it should make it slightly more obvious nonetheless

Also add v4.5.0 in versions and keep README.md pointing to v4.5.0 so that there are no broken stuff.