Tags to show which subsystem a patch is targeting

[destrex271]

Hi Team!

This might come in as a naive issue but I think that having tags related to the specific subsystem which a patch targets will be really helpful.

Although the current categorizations of Bugs, Clients etc do a great job but when we talk about specific patches, it would be really helpful if we can provide a tag highlighting the subsystem the patch majorly targets(eg: planner, optimizer, storage etc..)

There are certain edge cases where a patch might not fit within a set tag but this feature can really help in making it easier to understand the context of the patch for reviewers.

[JelteF]

Fixed by #69