docs(b-button): add accessibility section (bootstrap-vue#4770)

tmorehouse · web-flow · commit 6a0cdae5ee33 · 2020-02-14T22:02:52.000-04:00
diff --git a/src/components/button/README.md b/src/components/button/README.md
@@ -257,6 +257,16 @@ supported `<router-link>` related props.
 
 Note the `<router-link>` prop `tag` is referred to as `router-tag` in `bootstrap-vue`.
 
+## Accessibility
+
+When the `href` prop is set to `'#'`, `<b-button>` will render a link (`<a>`) element with attribute
+`role="button"` set and apropriate keydown listeners (<kbd>Enter</kbd> and <kbd>Space</kbd>) so that
+the link acts like a native HTML `<button>` for screen reader and keyboard-only users. When disabled,
+the `aria-disabled="true"` attribute will be set on the `<a>` element.
+
+When the `href` is set to any other value (or the `to` prop is used), `role="button"` will not be
+added, nor will the keyboad event listeners be enabled.
+
 ## See also
 
 - [`<b-button-group>`](/docs/components/button-group)
