RFC29: Proposal for mirror administration routines

Before this proposal, all tasks surrounding mirrors were manual and in free-text form. This RFC therefore outlines the definitions and guidelines surrounding both becoming but also maintaining and decommissioning a mirrors in a new format using TOML and GitLab.

https://lists.archlinux.org/archives/list/arch-dev-public@lists.archlinux.org/thread/2UMVBBDNRJE2RQZYGTE5GW4VWX5LUOC5/