Auto-label PRs based on changed files

[QuLogic]

PR summary

I believe this was not previously usable due to Actions permission changes, but now that the pull_request_target trigger exists, it should work again. Unfortunately, because it uses pull_request_target, there's no way to test until it's merged.

This is mainly to catch issues like #27628 which should have been labelled with Run cibuildwheel to show that it was broken.
Labelling the topics is a bit arbitrary, but I think I've covered enough of them.

PR checklist

• [n/a] "closes #0000" is in the body of the PR description to link the related issue
• [n/a] new and changed code is tested
• [n/a] Plotting related features are demonstrated in an example
• [n/a] New Features and API Changes are noted with a directive and release note
• [n/a] Documentation complies with general and docstring guidelines

[story645]

😍 Can you add the doc labels? the descriptions already have the maps https://github.com/matplotlib/matplotlib/labels

[QuLogic]

Done, except for tags and website, as I'm not sure there are any specific files for those.