actions/setup-lean

Stream: lean4 dev

[Julian Berman]

(I assume this doesn't already exist as I haven't seen it).

Anyone interested in collaborating on some simple setup-lean action for GH Actions? I've put some simple thing here: https://github.com/Julian/setup-lean/ which currently literally just installs elan the same way I was doing it in the project I need it for, but I probably will consider adding some additional small things -- presumably someone else will be interested in this.