consider a JOSS article for libGPML

[egonw]

See https://joss.theoj.org/, but while the articles are very brief, the review is really on the source code, and have a look at the feedback I got, which really got me into doing some serious hacking in my holidays: openjournals/joss-reviews#2558

[egonw]

Being drafted here: https://github.com/PathVisio/libGPML/tree/main/paper