PR Summary

It's not worth reviewing this until the rectangle rotation PR has been merged, but I'm opening for CI. Also still needs a test.

This builds on#21945 and#21830 and allows the bounding box of a PolygonSelector to be rotated:

importmatplotlib.pyplotaspltfrommatplotlib.widgetsimportPolygonSelectorfig=plt.figure()ax=fig.add_subplot()selector=PolygonSelector(ax,lambda*args:None,draw_bounding_box=True)selector.verts= [(0.3,0.3), (0.4,0.6), (0.7,0.9)]selector._box.add_state('rotate')plt.show()

PR Checklist

Tests and Styling

• Has pytest style unit tests (andpytest passes).
• IsFlake 8 compliant (installflake8-docstrings and runflake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry indoc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented indoc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs shouldbuild without error).