Provide documentation of older versions online #20
Description
I would be nice if older versions of the CGNS library also had documentation online.
For example, via https://cgns.github.io/CGNS_docs_<version> in addition to https://cgns.github.io/CGNS_docs_current
Now, I have to download the tag from https://github.com/CGNS/cgns.github.io, unpack the archive and browse locally.