Originally proposed in FluxML/Zygote.jl#1275 (comment)

This would -

1. add a nice and welcoming README for people visiting Flux's GitHub.
2. allow us to add common files like PR templates, CODE_OF_CONDUCT.md, and maybe issue templates to a central repository.

More on this here - https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file