Nest `.modal` styling directly under `.modal-open`
to avoid issues when bootstrap is nested.

Merge branch 'document-tooltip-flickering' of https://github.com/simPod/bootstrap into simPod-document-tooltip-flickering

* `svg:not(:root)` specificity is very high (https://github.com/necolas/normalize.css/issues/718)
* Bootstrap do not support SVG documents (See #26878)

Fixes #26227

Fixes #26281

Updates the properties and values for which we have existing variables to match our tooltips. Come 4.2, we'll create new tooltips for these.

- Splits the examples with code snippets
- Adds note about possible broken visuals

Closes #25813

* Redo input height on .form-control

- Use the already present -height variables on .form-control
- Consolidate the select size and multiple overrides into the .form-control base class instead of sm/lg modifiers
- Remove the Sass extends from input groups since it picks up too many selectors

* Prevent height on textareas

* Fix focus box shadow of custom ranges

* Put `:focus` selector right after `.custom-range`
* Remove unnecessary `outline: none`

* Fix box-shadow issues in IE/Edge

* Better align

* Fix thumb vertical positions in IE/Edge

* Fix incorrect formula of thumb vertical positions in Webkit

* Fix an incorrect comment

* Fix incorrect box-shadow-width

Now `.custom-control` will have height equal to `$font-size-base`
Fix custom checkbox and radio top position (we can't subtract rem from unit)
`$line-height-base - $custom-control-indicator-size` is not valid
Because `$line-height-base` is a unitless variable and `$custom-control-indicator-size`
is a unit (rem) variable

Merge branch 'examples-cleanup' of https://github.com/MartijnCuppens/bootstrap into MartijnCuppens-examples-cleanup

Merge branch 'box-shadow_issue_26377' of https://github.com/parammittal16/bootstrap into parammittal16-box-shadow_issue_26377

`docs-serve` was duplicated. Also, extend the existent `docs-serve` script for `docs-github-serve`.

closes #26586, closes #26587