[skip sauce]

https://www.youtube.com/watch?v=L-4VxEtWyRo

Added handling of aria-expanded=true/false to collapse.js, updated
documentation to include advice on making expand/collapse controls
accessible, updated examples and javascript documentation to use
aria-expanded and aria-controls (when targetting single collapsible
element, using ID rather than class selector)

Closes #14147.
Closes #14153.

Thanks to @collinanderson
Closes #14567

[skip sauce]

Fixes #14319: Prevent jumbotron reflow by ensuring padding of .container isn't interferred with by .jumbotron side padding

* move unrelated .btn-primary example out of the pills subsection
* remove excessive .nav-stacked example

Added apostrophes to 3 words to indicate possession (i.e. ownership of something) instead of plurality (i.e. multiples of something).

Fixes #14500

Also, link to the Mozilla bug in the relevant callout.

Refs #14362