Fix Hermes plugin entry point

[JWhitleyWork]

Summary

• Fix the hermes_agent.plugins entry point so github-app loads the package module instead of the register function directly
• Bump package version to 0.1.1 for the patch release
• Add a regression test that verifies the entry point loads a module with register
• Update the README release example to tag 0.1.1

Verification

• ruff format .
• ruff check .
• mypy
• pytest
• python -m build
• python -m twine check dist/*
• Verified editable entry point loads hermes_github_app_plugin module with register
• Installed the built wheel in a temporary venv and verified the entry point loads the module with register