moving rendering to rlberry

[JulienT01]

Description

Moving rendering to rlberry (to allow Chain and Gridworld moving back to rlberry_scool)

Checklist

• [x] My code follows the style guideline To check : black --check examples rlberry *py flake8 --select F401,F405,D410,D411,D412 --exclude=rlberry/check_packages.py --per-file-ignores="init.py:F401",
• [x] I have commented my code, particularly in hard-to-understand areas,
• [x] I have made corresponding changes to the documentation,
• [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,
• [x] If updated the changelog if necessary,
• [x] I have set the label "ready for review" and the checks are all green.

[github-actions[bot]]

Hello, The build of the doc succeeded. The documentation preview is available here: https://rlberry-py.github.io/rlberry/preview_pr