chore: Include env file dir as assets

[johannesvedder]

• Include the whole lib/envs folder inside the flutter_common package, so everyone can create their own .env.local without creating unstaged changes. Now you can create a copy of the existing .env.local.example and rename it to .env.local and replace the anon key with your own. Then run melos run dev:designer
• Move melos clean hook to custom melos run reset script
• Cleanup melos.yaml