* add 'lighter' and 'bolder' font weight classes
these are 2 special values for font weight, that will give their content a font-weight value of 100 more or less than their inherited font-weight.
probably doesn't fully fulfill this issue, https://github.com/twbs/bootstrap/issues/23969, but it's a start
* Update .stylelintrc
* add 'lighter' and 'bolder' variables per @mdo 's request.
* 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
- Only applies to textual inputs and textareas with `.form-control` and selects with `.custom-select`
- Wrap the feedback icons in a Sass variable option, $enable-validation-icons, so folks who theme can disable
- Update docs to summarize styles, mention the icons, include a textarea demo, and add mention of the Sass variable option to the Theming section
- Fixes#25656 where custom selects had the wrong focus shadow
- Fixes#26668 where custom selects had no inset shadow (also closes#26572 which had the wrong form classes on the first example anyway)
By applying the transition: CSS property only to classes that are
active during sliding, we avoid an unnecessary, non-zero-time
animation that although mostly invisible, does interfere with e.g.
z-index based parallax
