Adding support for proto extensions?

[dontonka]

I'm using protobuf and trying this plugin, but seems like it's lacking the support for extensionFields 🤔? Am I right, or misunderstanding something here?

[dontonka]

Seems like UnmarshalVT is compatible, but not MarshalVT.

Here is a snipet of UnmarshalVT implementation generated, for proto extensions (fieldNum is > than 1000 and fallback on the non-vtProto implementation)

		default:
			iNdEx = preIndex
			skippy, err := skip(dAtA[iNdEx:])
			if err != nil {
				return err
			}
			if (skippy < 0) || (iNdEx+skippy) < 0 {
				return ErrInvalidLength
			}
			if (iNdEx + skippy) > l {
				return io.ErrUnexpectedEOF
			}
			if (fieldNum >= 100) && (fieldNum < 10000) {
				err = proto.UnmarshalOptions{AllowPartial: true}.Unmarshal(dAtA[iNdEx:iNdEx+skippy], m)
				if err != nil {
					return err
				}
				iNdEx += skippy
			} else {
				m.unknownFields = append(m.unknownFields, dAtA[iNdEx:iNdEx+skippy]...)
				iNdEx += skippy
			}
		}