Add section to the WCS/celestial coordinates tutorial to demonstrate adding NE compass

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Requested by Julianne Dalcanton! It would be nice to add one more section (or to an existing section) a demo of how to add a little "N/E" right angle _| coordinate marker oriented with a specified coordinate frame, since that is a common use case.

https://learn.astropy.org/tutorials/celestial_coords1.html