docs: update catalog landing page and add github link

PiperOrigin-RevId: 646604510

Author: asyncliz

catalog/site/index.html

@@ -8,6 +8,18 @@
 {% block content %}
 
 <h1>Material Web</h1>
-<div class="subtitle">The official web component set for Material 3</div>
+<div class="subtitle">
+  <p>
+    <code>@material/web</code> is a library of
+    <a href="https://developer.mozilla.org/en-US/docs/Web/Web_Components" target="_blank">web components</a>
+    that helps build beautiful and accessible web applications.
+  </p>
 
-{% endblock %}
+  <p>
+    <a href="https://github.com/material-components/material-web/discussions/5642" target="_blank">
+      <strong>Note: MWC is in maintenance mode pending new maintainers.</strong>
+    </a>
+  </p>
+</div>
+
+{% endblock %}

catalog/src/components/top-app-bar.ts

@@ -71,6 +71,20 @@ export class TopAppBar extends SignalElement(LitElement) {
               on:interaction="pointerenter,focusin,pointerdown"
               import="/js/hydration-entrypoints/menu.js"
               id="menu-island">
+              <md-icon-button
+                title="GitHub repository"
+                aria-label="GitHub repository"
+                href="https://github.com/material-components/material-web"
+                target="_blank">
+                <md-icon>
+                  <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 98 96">
+                    <path
+                      fill-rule="evenodd"
+                      clip-rule="evenodd"
+                      d="M48.854 0C21.839 0 0 22 0 49.217c0 21.756 13.993 40.172 33.405 46.69 2.427.49 3.316-1.059 3.316-2.362 0-1.141-.08-5.052-.08-9.127-13.59 2.934-16.42-5.867-16.42-5.867-2.184-5.704-5.42-7.17-5.42-7.17-4.448-3.015.324-3.015.324-3.015 4.934.326 7.523 5.052 7.523 5.052 4.367 7.496 11.404 5.378 14.235 4.074.404-3.178 1.699-5.378 3.074-6.6-10.839-1.141-22.243-5.378-22.243-24.283 0-5.378 1.94-9.778 5.014-13.2-.485-1.222-2.184-6.275.486-13.038 0 0 4.125-1.304 13.426 5.052a46.97 46.97 0 0 1 12.214-1.63c4.125 0 8.33.571 12.213 1.63 9.302-6.356 13.427-5.052 13.427-5.052 2.67 6.763.97 11.816.485 13.038 3.155 3.422 5.015 7.822 5.015 13.2 0 18.905-11.404 23.06-22.324 24.283 1.78 1.548 3.316 4.481 3.316 9.126 0 6.6-.08 11.897-.08 13.526 0 1.304.89 2.853 3.316 2.364 19.412-6.52 33.405-24.935 33.405-46.691C97.707 22 75.788 0 48.854 0z" />
+                  </svg>
+                </md-icon>
+              </md-icon-button>
               <md-icon-button
                 id="theme-button"
                 @click="${this.onPaletteClick}"