Add instructions for citation

[chrislintott]

It would be useful to have clear instructions for how specutils should be cited in the literature, so that I can make sure authors are complying when editing their articles. Thanks!

[pllim]

Hello. While I do not have an immediate solution for you, this is the current situation of citation for this repo. cc @camipacifici @larrybradley @rosteen -- CITATION should have given you the answer but it currently links to an outdated Zenodo entry because the last GitHub Release failed to trigger an automated update via webhook. Furthermore, since the update is automated, we do not control the authors order, so if the order on Zenodo is incorrect, this repo would need a CITATION.cff file for accurate citation.

[pllim]

That said, even though unadvertised, I could find specutils in ASCL so that is also an alternative if you want.

https://ascl.net/1902.012