Add grpc plugin (#2758)

* Add grpc plugin

* remove stale readmes

client/grpc/response.go

@@ -0,0 +1,44 @@
+package grpc
+
+import (
+	"strings"
+
+	"go-micro.dev/v5/codec"
+	"go-micro.dev/v5/codec/bytes"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/encoding"
+)
+
+type response struct {
+	conn   *grpc.ClientConn
+	stream grpc.ClientStream
+	codec  encoding.Codec
+	gcodec codec.Codec
+}
+
+// Read the response.
+func (r *response) Codec() codec.Reader {
+	return r.gcodec
+}
+
+// read the header.
+func (r *response) Header() map[string]string {
+	md, err := r.stream.Header()
+	if err != nil {
+		return map[string]string{}
+	}
+	hdr := make(map[string]string, len(md))
+	for k, v := range md {
+		hdr[k] = strings.Join(v, ",")
+	}
+	return hdr
+}
+
+// Read the undecoded response.
+func (r *response) Read() ([]byte, error) {
+	f := &bytes.Frame{}
+	if err := r.gcodec.ReadBody(f); err != nil {
+		return nil, err
+	}
+	return f.Data, nil
+}