Add asset listing and delete

src/main/resources/templates/admin.html

@@ -24,7 +24,7 @@
             <p>Upload images to place on the broadcaster's overlay. Changes are visible to the broadcaster instantly.</p>
             <input id="asset-file" type="file" accept="image/*" />
             <button onclick="uploadAsset()">Upload</button>
-            <ul id="asset-list"></ul>
+            <ul id="asset-list" class="asset-list"></ul>
         </div>
     </section>
     <section class="overlay">