Initial docs (#61)

Add initial documentation site.

Co-authored-by: ambiguous48 <33713262+ambiguous48@users.noreply.github.com>

src/routes/__layout.svelte

@@ -2,4 +2,23 @@
   import "../app.css";
 </script>
 
+<div
+  class="sticky top-0 px-6 text-xl text-stone-500 w-full backdrop-blur border-b z-20"
+>
+  <div class="py-4 pr-4 flex justify-between">
+    <a href="/docs">
+      <span class="text-amber-600">Svelte</span> Headless UI
+    </a>
+    <a
+      href="https://github.com/rgossiaux/svelte-headlessui"
+      class="hover:text-black"
+    >
+      <svg viewBox="0 0 16 16" fill="currentColor" class="w-5 h-5">
+        <path
+          d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0016 8c0-4.42-3.58-8-8-8z"
+        />
+      </svg>
+    </a>
+  </div>
+</div>
 <slot />