chore: add protobuf

Makefile

@@ -1,10 +1,21 @@
+all: avro flatbuffers protobuf
+
 avro: twt-avro/gen.go
 twt-avro/gen.go: lextwt.avro
 	go tool avro gen -pkg twt_avro -encoders lextwt.avro > twt-avro/gen.go
 
 
-flatbuffers: twt-fbs/gen.go
-twt-fbs/gen.go: lextwt.fbs
+flatbuffers: twt-fbs/lextwt
+twt-fbs/lextwt: lextwt.fbs
 	flatc -o twt-fbs --go lextwt.fbs
 
-.ALL: avro flatbuffers
+protobuf: twt-pb/lextwt.pb.go
+twt-pb/lextwt.pb.go: lextwt.proto
+	protoc --proto_path=. \
+		--plugin=bin/protoc-gen-go \
+		--go_opt=paths=source_relative \
+		--go_opt="Mlextwt.proto=go.sour.is/lextwt-encoding/twt-pb;twt_pb" \
+		--go_out=twt-pb \
+		lextwt.proto 
+
+.PHONY: avro protobuf flatbuffers