RFR: 329: Add /cc command

[Robin Westberg]

On Tue, 9 Jun 2020 14:51:29 GMT, Erik Helin <ehelin at openjdk.org> wrote:

>> Hi all,
>> 
>> Please review this change that introduces the `/label` (aliased as `/cc`) command to add or remove additional labels
>> from a PR. The set of allowed labels are configured for each project. The command may be executed by the PR author as
>> well as other project Committers and above.  Best regards,
>> Robin
>
> Stellar work as always @rwestberg ✨ You thought about way more cases than I originally did, really nice work ��

Thanks for reviewing!

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PR: https://git.openjdk.java.net/skara/pull/645