25.2.0-trunk.445.0204.172429

feat: Use deb822 format for APT sources

- Replace `armbian-config.list` with `armbian-config.sources`. This
  holds the same information in a newer format, deb822. This does not
  affect `armbian.list`, but I could look at migrating that too if there
  is interest.
- Update `README.md` accordingly.