Winkel Tripel support?

[jphastings]

Could you add support for Winkel Tripel projection please?

I've tried both +prog=wintri with the core package, and prog.ESPGCOde(54042) (ref) with proj.Convert package, and neither seem to work. Though this projection is referenced in this repo I don't think it's implemented!

Is anyone able to add it? I'll take a look, in case it's simple, but I'd love a pointer if it's already done!

[m4rio31]

Just added the "+proj=wintri" as a Pull Request, waiting for approval.