Contribute tgtg-scanner.service

[Tqnsls]

This is not the perfect solution for implement the systemd unit file globally as the different distributions can have differently located python executables.
But I consider this is the first version to do this.

Pull Request Checklist:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Did you make your Pull Request on the dev branch?
• Does your submission pass tests? make test
• Have you lint your code locally prior to submission? make lint
• Could you build and run the docker image successfully? make image
• Could you create a running executable? make executable
• Have you added an explanation of what your changes do and why you'd like to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran manual tests with your changes locally?

[Der-Henning]

Hi @Tqnsls.
Thank you for your contribution.
As this is a very OS and use-case-specific topic I would rather like to add this as a tutorial in the wiki pages. The Readme is already too blown up for a quick start guide. I think I should start implementing something like readthedocs...

[Tqnsls]

Yes good idea.
I also was not happy with this as this is very specific but thought that itvwould help some people who are not into linux that much