For Markdown files, this isn't needed because the Markdown converter takes care of this.

- Add headings to examples section
- Clarify styles and customization options in examples
- Add dismiss buttons to all toasts
- Missing period added for consistency
- Update roles, tweak text

Also remove close button everywhere just let it when autohide is set to false

Reduces duplication and makes maintenance easier.

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

* 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