TNL-6743

TNL-6347

TNL-6440, TNL-6439

TNL-6369, TNL-6368

add_missing_semicolon

simple SpaceBeforeBrace

TNL-3821

This is a squash of 38 commits ending with
5b080f979d692804452400ac5bed9b17c50b001e

* updating vendor files
* updating class syntax (to new FA-based classes) for all UI elements
* correcting broken tests

SASS compilation variable conventions update, focusing on basic colors, baseline variable usage for padding and margins, ui-depth extends, along with other small fixes. The intent with this is to not have any user-facing impact, and instead move us closer toward having files that use our newer sass conventions.

LMS-2156

All the dialogs in the wiki are now accessible to screen readers.

Also, the "Switch to selected version" button did the odd thing of
reloading the page with the new version selected, but inside a dialog.
That is now fixed.

The merge dialog has a warning that looks kind of funky still, but you
can read it, unlike the previous code.

LMS-1337

Use the leanModal stuff to show the cheatsheet dialog in the wiki.

LMS-1303

- Doubled up :hover and :focus styling to improve a11y
- Increase contrast of certain UI elements for improved a11y
- Added some image alt text for a11y
- Changed video caption styling to blue and made them underline on hover and added a skip link before video for screenreaders.

Fixes Bugs:
- LMS-1336

with vision impairments

* bold text when active
* add in some extra text for screen readers

LMS-1306

Bourbon's box-shadow mixin has been deprecated, and they recommend to use the
official spec.

The official border-radius mixins were deprecated and removed in Bourbon 3.0.
https://github.com/thoughtbot/bourbon/pull/95

This reverts commit 2b5e8a49, reversing
changes made to db0549be.