Add the topic #local-first be added to yjs repository

[mgiorgino]

Checklist

[ ] Are you reporting a bug? Use github issues for bug reports and feature requests. For general questions, please use https://discuss.yjs.dev/
[ ] Try to report your issue in the correct repository. Yjs consists of many modules. When in doubt, report it to https://github.com/yjs/yjs/issues/

Is your feature request related to a problem? Please describe.
Searching for "#local-first" topic in github does not find yjs

Describe the solution you'd like
Searching for "#local-first" topic in github finds yjs

Describe alternatives you've considered
Searching for "#offline-first"

Additional context
Local-first and offline-first seems to be used interchangeably, but if someone only knows about one of them, it might not find yjs.