Run wheel builds on PRs when requested by a label

[QuLogic]

PR Summary

When I need to change the wheel building process, I need to push a copy to my fork's main, and then force push that away. But we can enable this on PRs by checking for a special label, reducing this extra work.

I used the "Run cibuildwheel" label, but if there's consensus for a better label name, we can use it. Then I'll actually create the label.

PR Checklist

Tests and Styling

• [n/a] Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• [n/a] New features are documented, with examples if plot related.
• [n/a] New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• [n/a] API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).

[jklymak]

I wonder if we want a prefix for this that makes it clear its private? _run cibuildwheel?

[dstansby]

I wonder if we want a prefix for this that makes it clear its private? _run cibuildwheel?

Only developers can add issues AFAIK, so I think this is fine? I added the label, and labelled this issue, just to double check it works. Looks like it does 👍 I'll merge without waiting for the wheel builds to finish, and feel free to change the colour of the label.