ci: add job for building binaries for releases
ci: add job for building binaries for releases

This will trigger a build of a linux, darwin and windows
build of protoc-gen-grpc-gateway and protoc-gen-swagger
on every new tag matching the semver regex.

gengo/grpc-gateway,improbable-io/grpc-gateway,improbable-io/grpc-gateway,gengo/grpc-gateway,grpc-ecosystem/grpc-gateway