Allow one to add markers from objects other than a table

[mwcraig]

While it is great that a table is an option, I often find myself creating a table just to use in add_markers. Accepting something like a Table or a numpy array would be convenient.

[pllim]

You mean, one array per column? Or one 2D array?

[mwcraig]

I meant accepting a numpy array instead of a Table (not that it would stop accepting tables, just that one could provide a numpy array instead). I'll try to flesh this out some more over the next week or so.

[pllim]

Actually got a request to create marker from regions (e.g., https://astropy-regions.readthedocs.io/en/stable/ or DS9 region file).