weekly releases needed

[xnox]

currently ubuntu-core-initrd vendors in lots of binaries at build time.

to ensure they are up to date we should trigger rebuilds of ubuntu-core-initrd, or have regular schedule when they release.

also given the success of automatic builds & releases of mantic branch, we should consider enabling automatic releases upon merged to focal & jammy branches too.

and probably have github action to automatically generate weekly commits and thus core-initrd releases.