Add basic searchbar (#5)

Co-authored-by: Tulir Asokan <tulir@maunium.net>

layouts/index.html

@@ -19,6 +19,7 @@
       To add your own plugins, send a pull request to
       <a href="https://github.com/maubot/plugins.maubot.xyz">github.com/maubot/plugins.maubot.xyz</a>
     </p>
+    <input class="search" type="text" id="search-input" placeholder="Search..." onkeyup="searchPlugins()">
   </header>
   <main>
     {{ range index $.Site.Data.plugins.official }}
@@ -32,5 +33,7 @@
     <a href="https://github.com/maubot/plugins">Website source</a>
     - Licensed under <a href="https://mau.fi/LICENSE">CC-BY-SA-4.0</a>
   </footer>
+
+  <script type="module" src="/index.js"></script>
 </body>
 </html>