New file structure for v2.0.0

[rodrigodelazcano]

Description

This PR edits the file structure for version v2.0.0 in the following way:

• Divide minigrid.py into sub-files for easier comprehension and keep them under core directory:
  • actions.py: class structure with the actions encodings
  • constants.py: constants in the environments such as object colors
  • grid.py: the grid class
  • mission.py: the mission space implementation
  • roomgrid.py: class for environments with rooms
  • world_object: object classes (Wall, Ball, Goal, Floor, ...)
• New utils directory for rendering files rendering.py and window.py

The package is also bumped to version v2.0.0 in the setup.py

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist:

• [ ] I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes