Add suggested format for recipe citation

[jwyg]

If we gather recipes from different people, projects and contexts, it would be nice to add a way to cite different recipes and acknowledge those who have authored/contributed to them.

Here's an example of how this could be done for a similar project from the Programming Historian: https://programminghistorian.org/en/lessons/beginners-guide-to-twitter-data

Here's an example from the Stanford Encyclopaedia of Philosophy:
https://plato.stanford.edu/entries/meister-eckhart/

And here's a suggestion for how to get a DOI for a Github repository: https://guides.github.com/activities/citable-code/

Here are further details on how we could apply for a (free) ISSN number if we wanted to make this into a more formal publication mechanism.
http://www.issn.org/wp-content/uploads/2018/01/GuidelinesExtranetPublisherRegistration-ENG.pdf
https://www.bl.uk/help/Get-an-ISBN-or-ISSN-for-your-publication

[jwyg]

Also discussed possibility of publishing on PubPub with @metasj: https://www.pubpub.org/