Improving protoc compilation for golang

### Describe the problem

Currently protoc throws an error `protoc-gen-go: unable to determine Go import path for "gtfs-realtime.proto"
` I believe this is in regard to no proper package name within the specification, though the specification on line 27 does have `package transit_realtime;` documentation at https://protobuf.dev/reference/go/go-generated-opaque/#package mention using `option go_package = "example.com/project/protos/fizz";` to declare it, which is missing in the file.

### Use cases

Easier compilation steps for golang applications using gtfs-rt specs :)

### Proposed solution

`:s/package transit_realtime;/option go_package = "github.com\/google\/transit";`
perhaps?

### Additional information

(not completely sure I used the correct template for this but yes)

Start with gtfs-realtime.proto and inspect the package declaration around line 27 alongside the Go generated-code package documentation linked in the issue. Run protoc with Go generation to reproduce the import-path error, then verify that the proposed package metadata allows Go applications to compile against the GTFS-realtime specification.

Written by the indexing model from the issue text.