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Fixes #14809.
Closes #14825.

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Closes #14772.

also includes tiny fix/clarification to two existing unit tests for the
.active class, adding data-toggle=“button” explicitly to the tested
buttons

Closes #14819.

Basically it's impossible to use the navigation if it's expanded. This will allow it to be scrollable so that the menus are accessable.

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Refs #13131.

Also, keep the html5 boilerplate link in the built CSS.

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Fixes #14251: Don't use hidden screen reader content in docs table so that Safari doesn't screw up overflow: hidden; content

Also adds unit tests for keyboard events.

Fixes #14468.