DOC: organize examples folder

[Gui-FernandesBR]

Pull request type

• Code changes (bugfix, features)
• Code maintenance (refactoring, formatting, tests)
• ReadMe, Docs and GitHub updates
• Other (please describe):

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally

Current behavior

We are running out of examples good enough to test our under-development features.

New behavior

I converted some old codes to jupyter notebooks (not the ideal, but will work fine for now), added then to the examples folder and also to the final documentation.

Breaking change

• Yes
• No

Additional information

• The data folder should be the placeholder for data in general, not the tests folder. We may change this in the future
• These new notebooks will help us to test some features and debug some flight simulations (hopefully). It helped me with the rocket drawing feature.

[review-notebook-app]

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See visual diffs & provide feedback on Jupyter Notebooks.

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[Gui-FernandesBR]

More flights were added here as a "positive side effect" of this PR: