Add support for easyp.gen.yaml files.

[rustwizard]

Could you add support for such config files? easyp.gen.yaml is a configuration file used by the easyp generate command to generate integration code. e.x. we have such project structure:

.
|── easyp.gen.ipam.yaml
|── easyp.gen.vm.yaml
|── easyp.yaml
|── proto
│   └── ipam
│           └── ipam.proto
│   └── vm
│           └── vm.proto
|── pkg
    └── ipam
    └── vm

easyp.yaml coud contains:

version: v1
directories:
  - proto/vm
  - proto/ipam
lint:
  use:
    - COMMENT_ENUM
    - COMMENT_ONEOF
    - COMMENT_RPC
    - COMMENT_SERVICE
deps:
  - github.com/googleapis/googleapis
  - github.com/bufbuild/protovalidate

easyp.gen.ipam.yaml:

version: v1
plugins:
  - name: go
    out: pkg/ipam
    opt: paths=source_relative

  - name: go-grpc
    out: pkg/ipam
    opt: paths=source_relative

easyp.gen.vm.yaml:

version: v1
plugins:
  - name: go
    out: pkg/vm
    opt: paths=source_relative

  - name: go-grpc
    out: pkg/vm
    opt: paths=source_relative

so then easyp generate --template easyp.gen.ipam.yaml proto/ipam should generate code into into pkg/ipam and
easyp generate --template easyp.gen.vm.yaml proto/vm into pkg/vm directories accordingly description in easyp.gen.* config files.