Missing dependencies section in readme

[dernasherbrezon]

I'm not a python dev, so had hard times figuring out what dependencies needed. It turned out 2 dependencies are required:

• systemd-python
• python3-yaml

I guess better to put advise installing them via apt-get or similar, otherwise users will install them via python dependency management, which require *-dev packages for compilation.

[kpfleming]

This program runs on any platform with Python 3 and systemd, not just Debian and derivatives, so it may not be practical to provide to provide distribution-specific package installation guidance for all of them as they use different package names and different tools. Also some users (like me) want to avoid the distribution packages and use the packages directly from pypi.org :-)

It would probably be safe to add a "Debian and derivatives" section and a "Fedora/CentOS/RHEL and derivatives" section, since those would cover the vast majority of users. Users on Gentoo, Arch, Nix, and other Linux distributions are often more familiar with solving these problems as they have to do it frequently.