add option for a background image, add default background

launch.html

@@ -440,7 +440,10 @@
          * Timeout trying to start the jitsi-meet-electron client
          */
         launchTimeout: 2000,
-
+        /*
+         * set wallpaper for webpage
+         */
+        backgroundImage: "assets/background.png",
         /*
          * Download URLs for jitsi-meet-electron client
          */
@@ -796,6 +799,21 @@
         return typeof value === "string" ? value : null;
       }
 
+      /* ============================================================
+       * BACKGROUND IMAGE
+       * ============================================================
+       */
+
+      function applyBackgroundImage() {
+        if (!CONFIG.backgroundImage) {
+          return;
+        }
+
+        document.body.style.backgroundImage = `url("${CONFIG.backgroundImage}")`;
+        document.body.style.backgroundSize = "cover";
+        document.body.style.backgroundPosition = "center";
+      }
+
       /* ============================================================
        * DOM elements
        * ============================================================
@@ -1436,6 +1454,7 @@ END:VCALENDAR`;
        */
 
       applyTranslations();
+      applyBackgroundImage();
       initialize();
     </script>
   </body>