add issue label config

[Stebalien]

for use with https://github.com/marketplace/actions/label-sync
related to protocol/web3-dev-team#90

[marten-seemann]

This PR seems incomplete, as it only adds the config file, but no instruction to actually copy the file (which, of course, is blocked by the fact that we currently can only copy files in .github/workflows, see #28 (comment)).
Can you convert it to a draft PR?

[Stebalien]

Yep, still working on it.

[galargh]

Hey! If we're still interested in labels synchronisation, I think we should do this through GitHub Management repos. It doesn't have native label support yet but it's planned - ipdxco/github-as-code#81.

In the meantime, we can create custom scripts to deal with the lack of native support. Here is an example of how we sync labels in js-libp2p and js-libp2p-peer-store repos https://github.com/libp2p/github-mgmt/blob/master/scripts/src/actions/sync-labels.ts.

I'm going to close this since there was no activity for a long time but please do let me know if you wanted set up label syncing in any repos, I'd be happy to assist.