feat: add grpc-test.json model for gRPC API request and response structures and update .gitignore to include the new file

Author: alexpmule

.gitignore

@@ -65,6 +65,7 @@ demo/models/flattened/*.json
 !demo/models/jldAsync26.json
 !demo/models/avro.json
 !demo/models/avro2.json
+!demo/models/grpc-test.json
 
 .idea/
 .sfdx