Fix route prefixes not stacking

src/server/services/WebServer/routes/RouteRegisterFactory.ts

@@ -48,7 +48,7 @@ export default class RouteRegisterFactory<M extends MiddlewareMethod<any> = neve
 	 */
 	public prefix<T extends MiddlewareMethod<any>>(prefix: string, middleware: T[], factory: RouteFactory<(M|T)>) {
 		let prefixBackup = this.pathPrefix;
-		this.pathPrefix = prefix;
+		this.pathPrefix += prefix;
 		this.group(middleware, factory);
 		this.pathPrefix = prefixBackup;
 	}