Chore: Scarb workspace, CI improvements

[julio4]

Issue(s): #86

Description

This don't add Starknet Foundry support but prepare for a upcoming partial support (where both scarb and snfoundry can be used).

Changes:

• Use scarb workspace to manage all listing: This allows to use other listings as dependencies (will be useful for components chapters)
• Update verifier script: Only test modified and added listing (deleting/renaming listings always failed)
• Add new script 'test_resolver': overwrite scarb test to run snforge test only if snforge is a dependency.
• Moved 'Contributing' part of the README inside CONTRIBUTING.md
• Improved documentation

There's an issue with running snforge with scarb's scripts with asdf: unknown command: snforge. Perhaps you have to reshim?. So snforge is not yet ready for use.

Checklist

• CI Verifier: Run cairo_programs_verifier successfully