Theme configuration through url

src/web/App.mjs

@@ -453,6 +453,7 @@ class App {
      * Searches the URI parameters for recipe and input parameters.
      * If recipe is present, replaces the current recipe with the recipe provided in the URI.
      * If input is present, decodes and sets the input to the one provided in the URI.
+     * If theme is present, uses the theme.
      *
      * @fires Manager#statechange
      */
@@ -491,6 +492,10 @@ class App {
             } catch (err) {}
         }
 
+        if (this.uriParams.theme) {
+            document.querySelector(":root").className = this.uriParams.theme;
+        }
+
         this.autoBakePause = false;
         window.dispatchEvent(this.manager.statechange);
     }