add rainbow theme

Author: usernameman12

public/css/themes.css

@@ -216,4 +216,14 @@
     --background-color: #330000;
     --border-color: #660000;
     --icon-color: #ffa07a;
+}
+
+:root.rainbow{
+    --primary-color: #ff0000;
+    --secondary-color: rgb(255, 128, 0);
+    --highlight-color: #e0d800;
+    --background-gradient: #26ff00, #00ffd5;
+    --background-color: #001aff;
+    --border-color: #7b00ff;
+    --icon-color: #ff0000;
 }

public/settings.html

@@ -62,6 +62,7 @@
           <option value="noctura">Noctura</option>
           <option value="sapphire">Sapphire</option>
           <option value="fire">Fire</option>
+          <option value="rainbow">Rainbow!</option>
         </select>
         <button type="button" id="save-theme-button" onclick="saveTheme()">
           Save Theme