Handle KeyboardInterrupt for inputscope-listener

[ulcuber]

Resolves #16

[suurjaak]

A good change, thank you, but I will have to decline this pull request, as the development happens in a private dev-branch. I will incorporate it there.

However, this would not resolve #16, as the problem with Ctrl-C is in main.py.

[ulcuber]

@suurjaak Yes, it does not resolve whole issue.
Where should open next pull requests? It would be useful to create CONTRIBUTING.md or DEVELOPERS.md

[suurjaak]

Over more than a decade of releasing open-source software, I think I've only ever received pull requests from like.. 2 people, so it has never really been a thing :)

But since pull requests cannot be disabled in GitHub anyway, users can always create one. In comparison to issues, they have the added benefit of code on the side, no matter whether and how the changes finally get incorporated.