BS compatibilitya11ydocshelp wanted
Description
We need accessibility docs which help explain how the end user of this library (the develop) can "close the gap" between what this library can and does provide in terms of accessibility and what is left up to the developer to implement in their specific usage.
For example, with things like Tooltip and Popover the "target" is outside of those components and thus cannot be affected by them, the developer will need to add aria-describedby/aria-labeledby and aria-haspopup="true" to the target element themselves. Similar, connecting Label and Input via the for prop on the Label and the id prop on the Input.
Bootstrap has something similar, but a little more generic: http://getbootstrap.com/docs/4.1/getting-started/accessibility/