Merge branch 'v4-dev-docs-hidden-show-replacement' of https://github.com/lamby/bootstrap into lamby-v4-dev-docs-hidden-show-replacement

Merge branch 'add-input-focus-variables' of https://github.com/kevinkucharczyk/bootstrap into kevinkucharczyk-add-input-focus-variables

Explicitly state the ordering of cards in card columns in the docs

Use @border-radius and add $nav-tabs-border-radius variable

Fixes #18705: Clarify removal of .help-text and update changes to .form-group for horizontal layouts

v4: Inverse table variants

Add disabled styling for .custom-select

Added explicit commentary to .card-* classes

Update Normalize to v4.0.0

- Change some things around, add some copy
- Include table variant styles for the inverse tables thanks to bg and color utils

Add GitHub issue template

Update overview.md

Jank card borders were too janky

Add $card-img-overlay-padding variable

Extract $carousel-icon-width variable

- Drops the experiment I had going for `box-shadow`-powered borders
- Reinstates regular `border` using existing variables

Fixes  #19097 and #19143. Nullifies #19828.

Use alphabetic order for the Components doc menu

[skip sauce]