feat(server): Add mypy-protobuf (#141)

Generates .pyi files for protobuf stubs which provide strong typing
information. Very helpful for IDE auto-completion, etc.

server/Makefile

@@ -3,9 +3,10 @@ flash_att_commit := 4d87e4d875077ad9efd25030efa4ab0ba92c19e1
 
 gen-server:
 	# Compile protos
-	pip install grpcio-tools==1.51.1 --no-cache-dir
+	pip install grpcio-tools==1.51.1 mypy-protobuf==3.4.0 'types-protobuf>=3.20.4' --no-cache-dir
 	mkdir text_generation_server/pb || true
-	python -m grpc_tools.protoc -I../proto --python_out=text_generation_server/pb --grpc_python_out=text_generation_server/pb ../proto/generate.proto
+	python -m grpc_tools.protoc -I../proto --python_out=text_generation_server/pb \
+		--grpc_python_out=text_generation_server/pb --mypy_out=text_generation_server/pb ../proto/generate.proto
 	find text_generation_server/pb/ -type f -name "*.py" -print0 -exec sed -i -e 's/^\(import.*pb2\)/from . \1/g' {} \;
 	touch text_generation_server/pb/__init__.py