add doc for protobuf update.

Signed-off-by: morvencao <[email protected]>

cloudevents/generic/options/grpc/protobuf/v1/README.md

@@ -0,0 +1,30 @@
+# CloudEvent gRPC Protobuf Definitions
+
+## Overview
+
+This repository includes the protobuf message and RPC method definitions for CloudEvent gRPC service, along with the corresponding Go code generated from these definitions.
+
+## Getting Started
+
+### Prerequisites
+
+Make sure you have the following tools installed:
+
+- [Protocol Compiler (protoc)](https://grpc.io/docs/protoc-installation/)
+- Go plugins for the protocol compiler:
+
+```bash
+$ go install google.golang.org/protobuf/cmd/protoc-gen-go
+$ go install google.golang.org/grpc/cmd/protoc-gen-go-grpc
+```
+
+### Updating CloudEvent gRPC Service
+
+1. Modify the `*.proto` files to reflect your desired changes.
+2. Run the following command to update the generated code:
+
+    ```bash
+    go generate
+    ```
+
+    This step is crucial to ensure that your changes are applied to both the gRPC server and client stub.

cloudevents/generic/options/grpc/protobuf/v1/cloudevent.proto

@@ -1,3 +1,7 @@
+// After making changes to the *.proto files, always run the following
+// command in current directory to update the generated code:
+// go generate
+
 syntax = "proto3";
 
 package io.cloudevents.v1;