Adding custom annotations

[azykophus]

Summary

This pull request introduces support for custom annotations required by a project that uses protoc-gen-doc. Specifically, it adds registration logic for new extensions so that these annotations are recognized and included in the generated Markdown documentation.

Details

• New Annotation Registration

  • Registers one or more new extensions in the relevant files (e.g., extensions.go).
  • Ensures that any proto file using these new annotations will have them parsed and displayed in generated documentation.

• Minimal Changes

  • Only a few lines are added to extension-processing logic.
  • No breaking changes for existing protoc-gen-doc features.

Rationale

Our project relies on specialized annotations that need to be visible in generated Markdown docs. Merging this upstream eliminates the need to maintain a long-term fork.

Testing

Generated documentation on sample proto files using the new annotations and confirmed they appear as expected.

Future Plans

• Once this PR is merged, the project can rely on the official protoc-gen-doc release rather than a patched version.
• We welcome any feedback or suggestions on how best to integrate these annotations.

Thanks for your time and review!