JS rules don't work with latest protobuf (3.21.x) repo

[srabraham]

Description

For some unknown reason, Google removed JavaScript support from the core protocolbuffers repo: protocolbuffers/protobuf#9874

This makes rules_proto_grpc unable to generate JavaScript protos. The correct new way to do things is to bring in https://github.com/protocolbuffers/protobuf-javascript and use it as a plugin to protoc.

The error I get currently with a rules_proto_grpc JS target is: "protoc-gen-js: program not found or is not executable"

Thanks for your work on this, Adam!

@alexeagle FYI

[srabraham]

Relevant: protocolbuffers/protobuf-javascript#127 (comment)

[aaliddell]

Thanks for the pointers on this, this is adopted in #178

[srabraham]

Awesome, thanks!