Update with Fern gRPC custom options (#2032)

Co-authored-by: Devin Logan <devinannlogan@gmail.com>

Author: kennyderek

fern/products/api-def/grpc-pages/services/grpc-services.mdx

@@ -416,4 +416,33 @@ service NotificationService {
 }
 ```
 
-gRPC services provide a strongly-typed, high-performance foundation for building distributed systems with clear contracts between clients and servers. 
+gRPC services provide a strongly-typed, high-performance foundation for building distributed systems with clear contracts between clients and servers.
+
+## Custom options
+
+Fern provides custom Protocol Buffer options to enhance your API Reference documentation and generated code.
+
+### API navigation name
+
+Use the `fern.summary` option to set an explicit display name for endpoints that's more user-friendly than the default RPC method name.
+
+<CodeBlock title="services.proto">
+```protobuf
+// Import Fern custom options
+import "fern/options.proto";
+
+service CommentsService {
+  // Description of the endpoint
+  rpc CreateComment(CreateCommentRequest) returns (CreateCommentResponse) {
+    option (google.api.http) = {
+      post: "/comments/v1/comments"
+      response_body: "comment"
+      body: "*"
+    };
+
+    // Display name shown in navigation
+    option (fern.summary) = "Create your comment";
+  }
+}
+```
+</CodeBlock>