Adding an "alone" mode

In "alone" mode (or single-player mode), WorkAdventure does not connect to the server at all.
In order to enter the "alone" mode, you need to add "?alone=true" to the URL.

"alone" mode can be useful for tutorials (First Time User Experience) where you want to explain how WorkAdventure works without being disturbed by other users.

front/src/Url/UrlManager.ts

@@ -35,7 +35,8 @@ class UrlManager {
     public pushRoomIdToUrl(room:Room): void {
         if (window.location.pathname === room.id) return;
         const hash = window.location.hash;
-        history.pushState({}, 'WorkAdventure', room.id+hash);
+        const search = room.search.toString();
+        history.pushState({}, 'WorkAdventure', room.id+(search?'?'+search:'')+hash);
     }
 
     public getStartLayerNameFromUrl(): string|null {