feat(grpc): skill for gRPC good practices, versioning and rollout using buf and code generation

[soulcodex]

Goal

1. Provide a skill fully focused on gRPC covering certain aspects, such as:
2. Readable, evolvable and easy to maintain protobuf contracts
3. buf library usage for code generation in different languages
4. buf constraints usage to validate protobuf inputs
5. Fosters good practices, versioning and backward compatibility
6. ConnectRPC whenever it make senses to avoid protobuf contracts duplication