adding IAU authority CRSs (for planets and moons)

[AndrewAnnex]

I am a planetary scientist interested in improving support for non-earth CRSs in various open source software libraries. There is an issue now with the OGC naming authority to add support for a pretty large list of CRSs for the planets and moons in the solar system (opengeospatial/NamingAuthority#212) defined by the IAU and the OGC's Planetary DWG. These CRSs are already contributed to PROJ (https://github.com/OSGeo/PROJ/search?q=IAU&type=commits). Since a number of javascript libraries depend on epsg.io's index however, it would be good to have parity with OGC NA in this project.

With this issue, I would like to gauge interest/ability to add the IAU authority and list of CRSs to epsg.io.

Considering that ESRI CRSs for some planets and moons are available already, it looks to me that this should be possible, although I couldn't find where in this repo those ESRI CRSs are added to make a PR myself.

A big potential issue to work out is that it may be troublesome to convert all the WKT CRSs to proj format properly which I haven't explored fully but is a potential blocker given the lossy conversions from WKT to proj.