Revert "Only mount the app directory for assets service"

This reverts commit f0e160c.

docker-compose.override.yml

@@ -34,8 +34,11 @@ services:
 
   assets:
     <<: *x-dev-defaults
-    volumes:
-      - ./app:/app/app
+    # As we have mounted the app directory into the container and esbuild expects the
+    # node_module folder therein: In case there is no node_module folder on the host machine
+    # run npm install to build node_modules in this mounted directory (app). Then just run npm run dev.
+    command: >
+      bash -c 'if [ ! -d "node_modules" ]; then npm install; fi && npm run dev'
 
   job-worker:
     <<: *x-dev-defaults