document the kinds of patches the repo is open to (#8900)
document the kinds of patches the repo is open to (#8900)

* document the kinds of patches the repo is open to 
google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf