Clintest

Changes
* Add initial support for optimization by teiesti in https://github.com/potassco/clintest/pull/31
* Add a py.typed by teiesti in https://github.com/potassco/clintest/pull/29
* Bugfixes by teiesti in https://github.com/potassco/clintest/pull/32

**Full Changelog**: https://github.com/potassco/clintest/compare/v0.1.0...v0.2.0

This is the first release of `clintest`. For details, please read [the documentation](https://potassco.org/clintest/). Have fun testing your `clingo` programs.