Add scale and compass to images

[teutoburg]

Feature request: add the option to include a WCS-driven compass/windrose as well as a scale for angular resolution to the RGB images.

[teutoburg]

Partially already supported in Astropy, see:
https://docs.astropy.org/en/stable/api/astropy.visualization.wcsaxes.add_scalebar.html#astropy.visualization.wcsaxes.add_scalebar

[teutoburg]

Compass might be obtained using:
https://matplotlib.org/stable/api/_as_gen/mpl_toolkits.axes_grid1.anchored_artists.AnchoredDirectionArrows.html#mpl_toolkits.axes_grid1.anchored_artists.AnchoredDirectionArrows

Actually, this should be added to Astropy, see previous comment...