MNT: add codecov integration

[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 run tests everytime but we don't see the code coverage percentage

New behavior

Adding codecoverage integration according to this: https://app.codecov.io/gh/RocketPy-Team/RocketPy/new.
This still needs to be tested before merging.

Breaking change

• Yes
• No

Additional information

None

[Gui-FernandesBR]

This is sad:

[codecov]

Welcome to Codecov 🎉

Once merged to your default branch, Codecov will compare your coverage reports and display the results in this comment.

Thanks for integrating Codecov - We've got you covered ☂️

[Gui-FernandesBR]

Well, this is working. Can we merge it and test it at least until the end of the year to evaluate if this is working properly?

[Gui-FernandesBR]

Can you confirm that you can access this report? https://app.codecov.io/gh/RocketPy-Team/RocketPy/tree/mnt%2Fadd-codecov-integration/?displayType=list