ENH: Add link and short description of how to report issues and bugs

[bsipocz]

If we add a link for how to report issues and bugs to the notebooks or pyvo or astroquery etc, it's more likely that people will actually report those.

Therefore I suggest to add a cell with a sentence of two and a link at the bottom/or top of each and every of our notebooks. Mention that the report is the most useful if a copy pasteable code to reproduce the issue is included (the concept of minimal reproducible example, can link this very nice scikit-learn doc [0] about it, but we can distill our own version of it, too, and link to that one instead)

[0] - https://scikit-learn.org/dev/developers/minimal_reproducer.html