feat: make success comments filterable

[balazsorban44]

Fixes #359

[jpsullivan]

I know this isn't particularly helpful, but my team has been running into this as well, and would love to see this merged in. If there's anything I can do to assist, please feel free to let me know!

[oljp]

LGTM. However I do think that documentation should be included for this filter as well.

[balazsorban44]

Of course! I can do, that, if you point me to the right place. 😊

[oljp]

I'm not an official maintainer, though if I were to assume I'd go ahead and drop the successFilter into the Options category of the README. https://github.com/semantic-release/github/blob/master/README.md#options, providing a brief description and maybe some example values.

[gr2m]

sorry for the delay with reviewing PRs. We are all pretty swamped right now, but how to find time to review the open PRs and onboard new maintainers soon

[raffis]

Any reason this is not merged? Currently I have the problem that if semantic-release with github gets added to an old repo with thousands of merged pr's, you end up with thousands of comments done by semantic-release. I wonder why this was not yet mentioned anywhere.
A filter would help in this case, we could add the released label manually to all merged pr's before introducing semantic-release.
Alternative solution might also the ability to specify a custom github search query.