move asdf-gctx here please

[chiefy]

Just made this but would like to have it here?

• https://github.com/chiefy/asdf-gctx

[smorimoto]

Consult this discussion post: https://github.com/orgs/asdf-community/discussions/57 This is the smoothest way to go. Of course I can do all the work for you, but it's done on a best effort basis. (I've been busy with work lately...)

[chiefy]

will do, thanks