Dev: Docker setup

[blocknotes]

🔧 Docker dev setup

# Run rails server on the dummy app (=> http://localhost:3000 to access to ActiveAdmin):
make up
# Enter in a Rails console (with the dummy app started):
make console
# Enter in a shell (with the dummy app started):
make shell
# Run the linter on the project (with the dummy app started):
make lint
# Run the test suite (with the dummy app started):
make specs
# Remove container and image:
make cleanup
# To try different versions of Ruby/Rails/ActiveAdmin edit docker-compose.yml
# For more commands please check the Makefile