🧑‍💻(docker) split frontend to another file

This commit aims at improving the user experience:
- Use a dedicated `Dockerfile` for the frontend
- Run the backend and frontend in "watch"/dev mode in Docker
- Do not start all Docker instances for small tasks

env.d/development/common.dist

@@ -3,6 +3,7 @@ DJANGO_ALLOWED_HOSTS=*
 DJANGO_SECRET_KEY=ThisIsAnExampleKeyForDevPurposeOnly
 DJANGO_SETTINGS_MODULE=people.settings
 DJANGO_SUPERUSER_PASSWORD=admin
+DJANGO_CORS_ALLOWED_ORIGINS=http://localhost:3000
 
 # Python
 PYTHONPATH=/app