Add plugin support to .protolint.yaml

[seriouspoop]

we should add something like plugins: yaml field same as in buf.yaml for linting it will be really helpful so that i can work with GitHub Actions, the workflow should read the config file and run the linting based on this yaml config including plugins

plugins:
  - plugin: buf-plugin-timestamp-suffix
    options:
      timestamp_suffix: _timestamp

[yoheimuta]

Thank you for creating an issue. That sounds nice 👍