fix(backend): allowjs in tsconfig.json

Prevents a warning in the backend unit tests about allowing JS code.

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

backend/tsconfig.json

@@ -16,6 +16,7 @@
     "strictPropertyInitialization": false,
     "resolveJsonModule": true,
     "useDefineForClassFields": false,
-    "preserveWatchOutput": true
+    "preserveWatchOutput": true,
+    "allowJs": true
   }
 }