Optimize project for usage as a git sub-module in developer's repository.

[DanieleVistalli]

compose-dx will evolve over time.

Ideally developers should not be copy-pasting stuff from the project but just using it a dependency a mid-term plan is about figuring out how compose-dx could be a git sub-module for a developer repo.

Ideal workflow:

1. Developer creates a project defining the workspace for a DX projects
2. Add compose-dx as a submodule to the project
3. Initializes the workspace (what this means needs to be defined)
4. Enjoys DX

When new compose-dx features are available the developer just "git pull"s changes and improves the experience.