proto importer for specs and muspecs

Now we offer 2 different ways to import specs from protos.

• protoc-gen-furo-muspecs which will generate muspecs
• protoc-gen-furo-specs which will generate specs

Usage: add this to your buf.gen.yaml

version: v1beta1
plugins:
  - name: furo-muspecs
    out: dist/muspecs
    opt: paths=source_relative

New features

• furo init with baseSpec v1.28.0
• pure grpc support, allows you to define pure grpc api's without bindings
• protoc-gen-furo-muspecs a protoc generator to generate muspecs
• protoc-gen-furo-specs a protoc generator to generate specs
• define * as body field with same behavior like HttpRule

Fixes

• spec2MuSpec with requestTypeSuffix
• init with FuroRequest as default requestTypeSuffix