ENH: Optional argument to show the plot in Function.compare_plots

[Gui-FernandesBR]

Pull request type

• Code changes (bugfix, features)

Checklist

• Tests for the changes have been added (not needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest tests -m slow --runslow) have passed locally
• CHANGELOG.md has been updated (if relevant)

Current behavior

Every time you call the the Function.compare_plots method, it will display the plot regardless of your intentions.

New behavior

Added a new argument to the method.
Plus updated the docstring, which was a bit old.

Breaking change

• No

Additional information

Quite easy to review this one.

[phmbressan]

Good work, I see no breaking changes here.

Sometimes it is useful to "manually edit" the fig and ax before showing.