Add the `topic-dataclasses` label

[picnixz]

There are quite a lot of recent issues on dataclasses and Nikita was interested in having this additional label.

• https://github.com/python/cpython/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc+dataclass+in%3Atitle
• https://github.com/python/cpython/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-desc+dataclass+in%3Atitle

I'm also tempted to suggest a topic-enum label but there has not been enough issues lately on enums so I don't think we need to have this label for now (the number of enum issues is also smaller compared to those on dataclasses).

[sobolevn]

My use-case: I subscribe to individual issues' topics on GitHub. I am very interested in dataclasses.py and I would love to get notifications about it.

If others don't want to polute the labels namespace, feel free to ignore me :) I will just read through issues from time to time (as I do now).

[JelleZijlstra]

cc @ericvsmith @carljm as maintainers of dataclasses.

Personally I'd probably favor a label for virtually any standard library module that gets a significant issue volume; I don't think the cost of a new label is very high. But others may disagree.

[carljm]

A label seems like a good idea to me; I remember wanting to find dataclasses issues and thinking it would be nice if there was a label.

[ericvsmith]

I agree with @carljm.

[hugovk]

I've created the label:

https://github.com/python/cpython/labels/topic-dataclasses

[picnixz]

Thanks to that label, I was able to add 45 opened issues to it. I think I'll now go through each of them and see if some of them can be closed. Thank you all!