Closes #13379.

Closes #11958 by rebasing & merging it

Update composer.json

Update minor version of alias to proper.

fixes #11099 - $.collapse() overrides the original dimension of the coll...

fixes #13296 Dropdown disappears with right-click on Firefox

rename jquery.js -> jquery.min.js since it's minified

Make variable deprecation notices visible in customizer

Added specificity note to docs per issue #13332

Wait for the expected target during a collapse

Document @icon-font-path & @icon-font-name more

Actually wait for the collapsed item to complete. If complete is called
with other target, instead of simply returning and do nothing, wait again
until the proper target triggers the event (otherwise this leaves collapse
in a broken state).

Remove unused javascript

Closes #11281 by merging it (after rebasing & resolving conflicts)

Add flexbox-based equal-height grid columns as an experimental example