Fixes #27595

* Tweak the accessibility/reduced motion text

include mention of carousel slides, remove the (now inaccurate, as Firefox 63 includes it too) mention that support is limited to Safari/macOS

xref https://github.com/twbs/bootstrap/issues/27525

* Add new callout for reduced motion

* Add variable to control prefers-reduced-motion media query support

* Add callout about prefers-reduced-motion to all components currently using animation which are affected

This change follows exactly what was done for the `$grays`, `$colors`, and `$theme-colors` lists in #23260. This allows for easy addition of new breakpoints or grid containers also.

Define new variable for card header color

In case we set `$body-bg` to a dark color, we have to keep table contrast relevant.

* #26967: Allow multiple ways of padding declaration for modal header
* #26976: split vertical and horizontal modal padding

Fixes #26886

* style: `_variables.scss` comments consistency

* style: `_variables.scss` spacing consistency

Blockquote footer font size is currently hardcoded to 80%, implying (in a comment) that this would result in the default font size. However, since the blockquote font size itself is variable, this is not necessarily true, and 80% of anything actually results in an arbitrary font size.

80% as a default is still fine.

fixes #26476

* add 'lighter' and 'bolder' font weight classes

these are 2 special values for font weight, that will give their content a font-weight value of 100 more or less than their inherited font-weight.

probably doesn't fully fulfill this issue, https://github.com/twbs/bootstrap/issues/23969, but it's a start

* Update .stylelintrc

* add 'lighter' and 'bolder' variables per @mdo 's request.

Fixes #26227

* Fix focus box shadow of custom ranges

* Put `:focus` selector right after `.custom-range`
* Remove unnecessary `outline: none`

* Fix box-shadow issues in IE/Edge

* Better align

* Fix thumb vertical positions in IE/Edge

* Fix incorrect formula of thumb vertical positions in Webkit

* Fix an incorrect comment

* Fix incorrect box-shadow-width

- Only applies to textual inputs and textareas with `.form-control` and selects with `.custom-select`
- Wrap the feedback icons in a Sass variable option, $enable-validation-icons, so folks who theme can disable
- Update docs to summarize styles, mention the icons, include a textarea demo, and add mention of the Sass variable option to the Theming section

- Fixes #25656 where custom selects had the wrong focus shadow
- Fixes #26668 where custom selects had no inset shadow (also closes #26572 which had the wrong form classes on the first example anyway)

Pagination move `.page-link:focus` outline value to variable `$pagination-focus-outline` so we can unset it via Sass and don't have to re-implement browser defaults