Add box-shadow utilities (#25758)

docs/4.0/utilities/shadows.md

@@ -0,0 +1,19 @@
+---
+layout: docs
+title: Shadows
+description:  Add or remove shadows to elements with `box-shadow` utilities.
+group: utilities
+toc: false
+---
+
+## Examples
+
+While shadows on components are disabled by default in Bootstrap and can be enabled via `$enable-shadows`, you can also quickly add or remove a shadow with our `box-shadow` utility classes. Includes support for `.shadow-none` and three default sizes (which have associated variables to match).
+
+{% capture example %}
+<div class="shadow-none p-3 mb-5 bg-light rounded">No shadow</div>
+<div class="shadow-sm p-3 mb-5 bg-white rounded">Small shadow</div>
+<div class="shadow p-3 mb-5 bg-white rounded">Regular shadow</div>
+<div class="shadow-lg p-3 mb-5 bg-white rounded">Larger shadow</div>
+{% endcapture %}
+{% include example.html content=example %}