[ftr] Edition details in about page

[daniel-jettka]

Is your feature request related to a problem? Please describe.
Details about the edition should be available in the Edirom, i.e. license, source code, contributors, ...

Describe the solution you'd like
The about page could hold this information, and the mechanism of frontend and backend infos could also be used for the edition details (relies on CITATION.cff for edition). It would also be possible to write the necessary information into the edition XML - not sure if this is feasible or desirable...