Add Collapse and Placeholders examples to cheatsheet

Introduced new sections for Collapse and Placeholders components in the cheatsheet example page, including navigation links and example usage for each component.

Update site/src/assets/examples/cheatsheet/index.astro

Update site/src/assets/examples/cheatsheet/index.astro

Update index.astro

Co-Authored-By: Copilot <175728472+Copilot@users.noreply.github.com>

Author: coliff

site/src/assets/examples/cheatsheet/index.astro

@@ -54,12 +54,14 @@ export const body_class = 'bg-body-tertiary'
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#button-group">Button group</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#card">Card</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#carousel">Carousel</a></li>
+          <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#collapse">Collapse</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#dropdowns">Dropdowns</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#list-group">List group</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#modal">Modal</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#navs">Navs</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#navbar">Navbar</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#pagination">Pagination</a></li>
+          <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#placeholders">Placeholders</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#popovers">Popovers</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#progress">Progress</a></li>
           <li><a class="d-inline-flex align-items-center rounded text-decoration-none" href="#scrollspy">Scrollspy</a></li>
@@ -879,6 +881,30 @@ export const body_class = 'bg-body-tertiary'
         `} />
       </div>
     </article>
+    <article class="my-3" id="collapse">
+      <div class="bd-heading sticky-xl-top align-self-start mt-5 mb-3 mt-xl-0 mb-xl-2">
+        <h3>Collapse</h3>
+        <a class="d-flex align-items-center" href={getVersionedDocsPath('components/collapse')}>Documentation</a>
+      </div>
+
+      <div>
+        <Example showMarkup={false} code={`
+        <p class="d-inline-flex gap-1">
+          <a class="btn btn-primary" data-bs-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
+            Link with href
+          </a>
+          <button class="btn btn-primary" type="button" data-bs-toggle="collapse" data-bs-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
+            Button with data-bs-target
+          </button>
+        </p>
+        <div class="collapse" id="collapseExample">
+          <div class="card card-body">
+            Some placeholder content for the collapse component. This panel is hidden by default but revealed when the user activates the relevant trigger.
+          </div>
+        </div>
+        `} />
+      </div>
+    </article>
     <article class="my-3" id="dropdowns">
       <div class="bd-heading sticky-xl-top align-self-start mt-5 mb-3 mt-xl-0 mb-xl-2">
         <h3>Dropdowns</h3>
@@ -1322,6 +1348,36 @@ export const body_class = 'bg-body-tertiary'
         `} />
       </div>
     </article>
+    <article class="my-3" id="placeholders">
+      <div class="bd-heading sticky-xl-top align-self-start mt-5 mb-3 mt-xl-0 mb-xl-2">
+        <h3>Placeholders</h3>
+        <a class="d-flex align-items-center" href={getVersionedDocsPath('components/placeholders')}>Documentation</a>
+      </div>
+
+      <div>
+        <Example showMarkup={false} code={`
+        <div class="card" aria-hidden="true">
+          <svg aria-label="Placeholder" class="bd-placeholder-img card-img-top" height="180" preserveAspectRatio="xMidYMid slice" role="img" width="100%" xmlns="http://www.w3.org/2000/svg">
+            <title>Placeholder</title>
+            <rect width="100%" height="100%" fill="#868e96"></rect>
+          </svg>
+          <div class="card-body">
+            <div class="h5 card-title placeholder-glow">
+              <span class="placeholder col-6"></span>
+            </div>
+            <p class="card-text placeholder-glow">
+              <span class="placeholder col-7"></span>
+              <span class="placeholder col-4"></span>
+              <span class="placeholder col-4"></span>
+              <span class="placeholder col-6"></span>
+              <span class="placeholder col-8"></span>
+            </p>
+            <a class="btn btn-primary disabled placeholder col-6" aria-disabled="true"></a>
+          </div>
+        </div>
+        `} />
+      </div>
+    </article>
     <article class="my-3" id="popovers">
       <div class="bd-heading sticky-xl-top align-self-start mt-5 mb-3 mt-xl-0 mb-xl-2">
         <h3>Popovers</h3>