Make overlay MUC wider

sass/_variables.scss

@@ -118,7 +118,7 @@ $mobile_portrait_length: 480px !default;
     --chatroom-head-description-border-left: 0px;
     --chatroom-head-description-padding-left: 0px;
     --chatroom-head-border-bottom: 0px;
-    --chatroom-width: 400px;
+    --chatroom-width: 500px;
     --chatroom-correcting-color: #fadfd7; // lighten($red, 30%)
     --chatroom-badge-color: var(--chatroom-head-color);
     --chatroom-badge-hover-color: var(--chatroom-head-color-dark);