Cater for the library usecase.
- Changed server start/await API to be more practical
- Revamped docs
- Added example unittest
- Improved Conf API ergonomy
- Added a dump_prefix config
- Switched mqttrs to upstream/crates.io release
- Updated tokio-util to 0.3
There is still plenty to do, but these changes were enough to convert my unittest to call the
library instead of running the binary.