Release v5.3.0-alpha1 (#37661)

* Bump version to 5.3.0-alpha1

* Dist

* Add docs versions updates

* Update note in homepage hero

Co-authored-by: Mark Otto <markdotto@gmail.com>

site/content/docs/5.3/examples/sticky-footer/index.html

@@ -0,0 +1,24 @@
+---
+layout: examples
+title: Sticky Footer Template
+extra_css:
+  - "sticky-footer.css"
+html_class: "h-100"
+body_class: "d-flex flex-column h-100"
+include_js: false
+---
+
+<!-- Begin page content -->
+<main class="flex-shrink-0">
+  <div class="container">
+    <h1 class="mt-5">Sticky footer</h1>
+    <p class="lead">Pin a footer to the bottom of the viewport in desktop browsers with this custom HTML and CSS.</p>
+    <p>Use <a href="{{< docsref "/examples/sticky-footer-navbar" >}}">the sticky footer with a fixed navbar</a> if need be, too.</p>
+  </div>
+</main>
+
+<footer class="footer mt-auto py-3 bg-light">
+  <div class="container">
+    <span class="text-muted">Place sticky footer content here.</span>
+  </div>
+</footer>

site/content/docs/5.3/examples/sticky-footer/sticky-footer.css

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+/* Custom page CSS
+-------------------------------------------------- */
+/* Not required for template or sticky footer method. */
+
+.container {
+  width: auto;
+  max-width: 680px;
+  padding: 0 15px;
+}