feat(docs): add focus-visible paragraph in accessibility page

site/docs/4.3/getting-started/accessibility.md

@@ -47,6 +47,11 @@ For visually hidden interactive controls, such as traditional "skip" links, `.sr
 
 Boosted includes support for the [`prefers-reduced-motion` media feature](https://drafts.csswg.org/mediaqueries-5/#prefers-reduced-motion). In browsers/environments that allow the user to specify their preference for reduced motion, most CSS transition effects in Boosted (for instance, when a modal dialog is opened or closed, or the sliding animation in carousels) will be disabled.
 
+[comment]: # Boosted mod
+### Focus visibility
+
+Boosted includes a [focus-visible polyfill](https://github.com/WICG/focus-visible) to ensure an enhanced focus visibility for keyboard users while shutting down focus styles on active state.
+
 ## Additional resources
 
 - [Web Content Accessibility Guidelines (WCAG) 2.0](https://www.w3.org/TR/WCAG20/)
@@ -57,3 +62,4 @@ Boosted includes support for the [`prefers-reduced-motion` media feature](https:
 - ["HTML Codesniffer" bookmarklet for identifying accessibility issues](https://github.com/squizlabs/HTML_CodeSniffer)
 - ["aXe core" extension for identifying accessibility issues](https://github.com/dequelabs/axe-core/blob/master/doc/projects.md)
 - [Orange accessibility guidelines](http://a11y-guidelines.orange.com/home_EN/index.html)
+- [MDN focus-visible documentation](https://developer.mozilla.org/en-US/docs/Web/CSS/:focus-visible)

site/docs/4.3/getting-started/introduction.md

@@ -52,7 +52,7 @@ We use [jQuery's slim build](https://blog.jquery.com/2016/06/09/jquery-3-0-final
 
 Curious which components explicitly require jQuery, our JS, and Popper.js? Click the show components link below. If you're at all unsure about the general page structure, keep reading for an example page template.
 
-Our `boosted.bundle.js` and `boosted.bundle.min.js` include [Popper](https://popper.js.org/), but not [jQuery](https://jquery.com/). For more information about what's included in Boosted, please see our [contents]({{ site.baseurl }}/docs/{{ site.docs_version }}/getting-started/contents/#precompiled-boosted) section.
+Our `boosted.bundle.js` and `boosted.bundle.min.js` include [Popper](https://popper.js.org/) and [focus-visible's Polyfill](https://github.com/WICG/focus-visible), but not [jQuery](https://jquery.com/). For more information about what's included in Boosted, please see our [contents]({{ site.baseurl }}/docs/{{ site.docs_version }}/getting-started/contents/#precompiled-boosted) section.
 
 <details>
 <summary class="text-primary mb-3">Show components requiring JavaScript</summary>