fedrq 0.15.0

Added:

- backends dnf: add `load_filelists()` implementation. This makes sure that
  systems with `dnf >= 4.19.0` can, for example, use `-L always` to load
  filelists.

Changed:

- doc: revamp and cleanup

Fixed:

- changelogs: fix off-by-one error with `--entry-limit` flag