Make "Test with:" support more formats

[axel-h]

Follow-up from #184

GitHub URLs are shown in a short format, even is the actual description text contains a longer format. That can be confusing, as the "test with" does not work then, even if thing look right.

• Add support for https://github.com/<org>/<repo>/pull/<id> because GitHub URLs are shown in the short format <org>/<repo>#<id> in the GitHUb GUI, but are stored in the description test in the long format.
• When copy/pasting parts from descriptions from other PRs, link can also end up in the format [<org>/<repo>#<id>](https://github.com/<org>/<repo>/pull/<id>), so supporting a format [<some text>](https://github.com/<org>/<repo>/pull/<id>) might also be worth adding at a later stage for even more convenience.