Create ExpandButton.svelte

src/components/ExpandButton.svelte

@@ -0,0 +1,27 @@
+<script>
+  import { createEventDispatcher } from 'svelte'
+
+  const dispatch = createEventDispatcher()
+
+  let expanded = false
+</script>
+
+<button
+  class="w-4 h-4 flex justify-center align-middle text-gray-500 hover:text-blue-600 dark:text-gray-100 dark:hover:text-blue-600 shrink-0"
+  on:click={() => {
+    expanded = !expanded
+    dispatch('click', { state: expanded })
+  }}
+  area-label={expanded ? 'Collapse' : 'Expand'}
+>
+  <svg
+    class="w-4 h-4"
+    class:rotate-90={expanded}
+    fill="none"
+    stroke="currentColor"
+    viewBox="0 0 24 24"
+    xmlns="http://www.w3.org/2000/svg"
+  >
+    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"></path>
+  </svg>
+</button>