Add @garymoon to MAINTAINERS (#24752)

Add @garymoon to MAINTAINERS (#24752)

Hi all.

I would like to apply to be a maintainer please. I have [four accepted
PRs](https://github.com/go-gitea/gitea/pulls?q=is%3Apr+author%3Agarymoon)
(such as they are), sign my commits, and have MFA enabled everywhere. My
hope is to continue with code contributions where I can (I'm not a
developer, just a wannabe), take some work off kdumont's hands, and
contribute on the infrastructure side where there is room 💚 :tea:

Thank you!