Containerized dev and test environment

This PR will significantly improve development experience.

App can be run with single command: docker compose up
- Database is created and seeded automatically, no need to use npm scripts anymore
- Fast reloading is supported so you can modify code and see changes instantly both in backend and frontend
Test containers can be launched with single command (in frontend's folder with npm run test-setup)
- Test containers are separate from dev containers, so they can be run simultaneously
- Running tests doesn't mess dev db anymore
- Database is initialised every time when test setup is started
Bonus: Added adminer which allows to view and modify database from browser
- Just navigate to localhost:8083 and login with info found in readme

Ohtuilmo / ohtuilmo