Systemdlint

72 - Add special values for RuntimeWatchdogSec setting

thanks to wandering-tales

What's Changed
* Align InvalidValue settings to systemd documentation by zgauci in https://github.com/priv-kweihmann/systemdlint/pull/69


**Full Changelog**: https://github.com/priv-kweihmann/systemdlint/compare/1.3.1...1.3.2

Fix

- Fix ExecValue prefix check 68

New

- 62 new `--messageformat` CLI option

Fixes

- 65 proper validation of `--sversion` input

Misc

- 65 drop support for python < 3.8

New

- 55 - systemd 2.50 support

New

- 54 - Python 3.10 support