New issue by Duncaen on void-packages repository

https://github.com/void-linux/void-packages/issues/39166

Description:
It might be nice to create a xbps repository for packages that are supposed to be used by xbps-src only, like `-bootstrap` packages and maybe `chroot-*` packages.

This would avoid them showing up in default repository and avoids users installing `chroot-*` packages due to virtual packages by accident.

We would add `repository="bootstrap"` to templates and add that repository to the repository pool in `xbps-src`.