(v3.3.0) Sinergym documentation enhancement

[AlejandroCN7]

Description

This PR enhances the overall Sinergym documentation. It includes new information such as the default observation and action variables for each building. Naturally, these variables can be modified as needed.

Types of changes

• [ ] 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 change)
• [x] Documentation (update in the documentation)
• [ ] Improvement (of an existing feature)
• [ ] Others

Checklist:

• [x] I've read the CONTRIBUTION guide (required)
• [x] My change requires a change to the documentation.
• [ ] I have updated the tests.
• [x] I have updated the documentation accordingly.
• [ ] I have reformatted the code using autopep8 second level aggressive.
• [ ] I have reformatted the code using isort.
• [ ] I have ensured cd docs && make spelling && make html pass (required if documentation has been updated.)
• [ ] I have ensured pytest tests/ -vv pass. (required).
• [ ] I have ensured pytype -d import-error sinergym/ pass. (required)

Changelog:

• Update all documentation sections.
• Update README.md.
• Update INSTALL.md.
• Use cases notebooks update.