Add `tabindex="-1"` and `aria-disabled="true"` to disabled link

We use the official HTML validator for HTML validation, and we don't really use any of the htmllint features.

Fixes #27595

* remove jobs link
* specify a link in the BrowserStack image

this is the opposite of `.text-nowrap`, and a forces elements to wrap onto new lines.

One use case for this is extra long button text. Bootstrap buttons by default do no wrap, so this class could be used to override that behavior.

This should be faster.

After 3256a2c2, blc honored robots.txt thus it didn't crawl anything.
Ignore robots.txt to work around the issue.

`0.0.0.0` has issues on Windows.

diff credits: @client9

* 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