Added Buf files

[Jonathan-Landeed]

Adding these files allows the project to be uploaded to the buf.build BSR. Apparently it won't work as a remote plugin, but it's still nice as a dependency for import "patch/go.proto"; in Buf projects.

See bufbuild/plugins#858

[ydnar]

Thanks! Is this a registry of Buf plugins? Should I create a username there to register this?

[ydnar]

I created #174 which replicates this PR using an official distribution at https://buf.build/alta/protopatch.

Do you have a sense for what should be in the README to document how Buf users would use this?

  - local: protoc-gen-go-patch
    out: gen
    opt:
      - paths=source_relative
      - plugin=go

[ydnar]

If you want to grab the changes from #174 and incorporate them here, I'd also like to see tests (local, CI) that validate Buf works.