WebSocketListener: add app field getter

package.json

@@ -1,6 +1,6 @@
 {
   "name": "wms-core",
-  "version": "0.17.0",
+  "version": "0.17.1",
   "description": "Node web framework",
   "repository": "git@gitlab.com:ArisuOngaku/wms-core.git",
   "author": "Alice Gaudon <alice@gaudon.pro>",

src/WebSocketListener.ts

@@ -9,6 +9,10 @@ export default abstract class WebSocketListener<T extends Application> {
         this.app = app;
     }
 
+    protected getApp(): T {
+        return this.app;
+    }
+
     public abstract path(): string;
 
     public abstract async handle(socket: WebSocket, request: IncomingMessage, session: Express.SessionData): Promise<void>;