GitHub labeler: label more files

[jbampton]

These are some of the config files for the linters/tests that run

[jbampton]

See in refs #6204 that the pull request was not labeled.

Best to have labels for all files / folders.

[dearblue]

I think it's a bit different to belong to the build label.

🤔 Since I think the number is small and not a noteworthy classification, I propose miscellaneous and cast my vote.
Other label names I can think of are edit, coding, and utility.
If there is another preferred proposal, I may vote for that one.

[jbampton]

Thanks @dearblue I went with miscellaneous for the new label

[jbampton]

Hey @matz

I forgot to mention that we need to add the new label for miscellaneous on the repo labels page here:

https://github.com/mruby/mruby/labels

Thanks

[matz]

Done.