- fix naming of left/right controls
- drop the absolute positioning of things and rely on only 3d transforms
- remove img styles and require classes to avoid inline-block line-height stuff

- Un-nests .carousel-item
- Appends .carousel-item- to .left, .right, .next, and .prev
- Chain .carousel-item to .active where approproriate

* Add some flexbox nav components
  - Includes .nav-justified for inline, tab, and pill nav components
  - Includes example of using the flex utils (.d- and .flex-items-) for centered nav
* redo heading hierarchy a bit

* Darken dismiss icon opacity
* Darken text on active list group items
* Darken light gray for accessibility/contrast, then update gray and dark gray to match

* Fix bug with dropdown tab links not deactivating when other tab or dropdown link is clicked

* Revise bug fix for more stability

[skip sauce]
[skip validator]

Update Normalize to v5.0.0.

Fix pagination underline

switch to rgba for list-group border color

renamed modal-title-padding to modal-header-padding

Fixes #21094: Move text-decoration override from the default link state to the hover/focus state so it can override the global styles properly

Refs https://bugs.chromium.org/p/chromium/issues/detail?id=510079
Closes #21120

[skip sauce]

Feature/omit xs from grid

Update visual tests.

Change .tag print styles to .badge.

Fix padding on .bg-faded demo.

it's → its

Small grammar fix.