v5: Forms update (#28450)

* Initial spike of consolidated form checks

* Stub out forms rearrangement

- Prepping to drop non-custom file and range inputs
- Prepping to merge custom and native checks and radios (with switches)
- Prepping to merge custom select with form select
- Moving docs arround so forms has it's own area given volume of CSS

* Move input group Sass file to forms subdir

* Start to split and move the docs around

* Simpler imports

* Copyediting

* delete overview file

* Remove commented out code

* remove the custom-forms import

* rewrite flex-check as form-check, replace all custom properties

* Remove old forms doc

* stub out new subpage link section

* update migration guide

* Update nav, forms overview in page nav, and descriptions

* fix check bg position

* fix margin-top calculation

* rename .custom-select to .form-select

* Update validation styles for new checks

* add some vertical margin, fix inline checks

* fix docs examples

* better way to do this contents stuff, redo the toc while i'm at it

* page restyle for docs while here

* un-callout that, edit text

* redo padding on toc

* fix toc

* start to cleanup checks docs

* Rewrite Markdown tables into HTML

* Redesign tables, redo their docs

* Replace Open Iconic icons with custom Bootstrap icons

* Redesign the docs navbar, add a subheader, redo the sidebar

* Redesign docs homepage a bit

* Simplify table style overrides for docs tables

* Simplify docs typography for page titles and reading line length

* Stub out icons page

* Part of sidebar update, remove migration from nav.yml

* Move toc CSS to separate partial

* Change appearance of overview page

* fix sidebar arrow direction

* Add footer to docs layout

* Update descriptions

* Drop the .form-group class for margin utilities

* Remove lingering form-group-margin-bottom var

* improve footer spacing

* add headings to range page

* uncomment form range css

* Rename .custom-range to .form-range

* Drop unused docs var

* Uncomment the comment

* Remove unused variable

* Fix radio image sizing

* Reboot update: reset horizontal ul and ol padding

* de-dupe IDs

* tweak toc styles

* nvm, fix dropdown versions stuff

* remove sidebar nav toggle for now

* broken html

* fix more broken html, move css

* scss linting

* comment out broken helper docs

* scope styles

* scope styles

* Fixes #25540 and fixes #26407 for v5 only

* Update sidebar once more

* Match new sidenav order

* fix syntax error

* Rename custom-file to form-file, update paths, update migration docs for previous changes in #28696

* rename back

* fix size and alignment

* rename that back too

1 files changed, 62 insertions, 0 deletions

diff --git a/site/content/docs/4.3/forms/select.md b/site/content/docs/4.3/forms/select.md
new file mode 100644
index 000000000..a3a8198ba
--- /dev/null
+++ b/site/content/docs/4.3/forms/select.md
@@ -0,0 +1,62 @@
+---
+layout: docs
+title: Select
+description: Customize the native `<select>`s with custom CSS that changes the element's initial appearance.
+group: forms
+toc: true
+---
+
+## Default
+
+Custom `<select>` menus need only a custom class, `.form-select` to trigger the custom styles. Custom styles are limited to the `<select>`'s initial appearance and cannot modify the `<option>`s due to browser limitations.
+
+{{< example >}}
+<select class="form-select">
+  <option selected>Open this select menu</option>
+  <option value="1">One</option>
+  <option value="2">Two</option>
+  <option value="3">Three</option>
+</select>
+{{< /example >}}
+
+## Sizing
+
+You may also choose from small and large custom selects to match our similarly sized text inputs.
+
+{{< example >}}
+<select class="form-select form-select-lg mb-3">
+  <option selected>Open this select menu</option>
+  <option value="1">One</option>
+  <option value="2">Two</option>
+  <option value="3">Three</option>
+</select>
+
+<select class="form-select form-select-sm">
+  <option selected>Open this select menu</option>
+  <option value="1">One</option>
+  <option value="2">Two</option>
+  <option value="3">Three</option>
+</select>
+{{< /example >}}
+
+The `multiple` attribute is also supported:
+
+{{< example >}}
+<select class="form-select" multiple>
+  <option selected>Open this select menu</option>
+  <option value="1">One</option>
+  <option value="2">Two</option>
+  <option value="3">Three</option>
+</select>
+{{< /example >}}
+
+As is the `size` attribute:
+
+{{< example >}}
+<select class="form-select" size="3">
+  <option selected>Open this select menu</option>
+  <option value="1">One</option>
+  <option value="2">Two</option>
+  <option value="3">Three</option>
+</select>
+{{< /example >}}