Add reference publication equivalent

[physikerwelt]

describedBySource seems to be a reasonable equivalent to referencePublication

[dgarijo]

+1. Supporting example: https://www.wikidata.org/wiki/Q118564029

[physikerwelt]

@moranegg, do you know, by chance, who could review this PR? It has been a while.

[dgarijo]

I guess mine could be considered a review?

[moranegg]

Hi @physikerwelt for the ping.
We have a big delay with the maintenance of CodeMeta because of lack of time and a more standardized community governance which doesn't make things faster :)

Thanks @dgarijo for the review.
For me it's a go to merge, but I'm answering this on my phone..
Will get back to you ASAP.