RFR: pr-bot: add contributors to summary

[Robin Westberg]

On Wed, 12 Feb 2020 10:55:23 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that adds information about contributors to the PR
> body. Please note that we now have to run an extra pass with the `CheckWorkItem`
> to make it possible to update the PR body based on the results from the
> `CommandWorkItem`.
> 
> Testing:
> - added a new unit test
> - `make test` passes on Linux x64
> 
> Thanks,
> Erik

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/429