archlinux-wsl repo & automation setup

Hi 👋,

Following the acceptance of the related RFC, I'm opening this issue to list & track the next implementation steps for the official Arch Linux WSL image:

• Create the https://gitlab.archlinux.org/archlinux/archlinux-wsl repo
• Give me permissions over it 👼
• Add secure runners for the repo (for the scheduled CI publishing the monthly image)
• WSL image mirroring (!924 (merged))
• Set up automatic monthly PRs to https://github.com/microsoft/WSL in order to update the DistributionInfo.json file on new image releases (once it has been initially added).

I remain available 🤗