Add prototool format

clang-format is pretty limited in its formatting options of *.proto, prototool is much more complete

**Describe the solution you'd like**
Add the prototool (https://github.com/uber/prototool) formatter as an option

**Describe alternatives you've considered**
Have not tried any alternatives, I don't believe there is an alternative?

No file or test is named in the issue. Start by tracing the existing clang-format integration and how formatter options are registered, then determine where prototool should be added for *.proto files. Done means the new formatter option is available and formats protobuf files through the plugin.

Written by the indexing model from the issue text.