Add stable releases and semantic versioning support

[subhobhai943]

Summary

This PR addresses issue #39 by implementing stable releases and semantic versioning for pplx-kernels. Users can now pin to specific versions instead of commit SHAs, making the project more stable and easier to manage.

Changes Made

1. Automated Release Workflow

• Added .github/workflows/release.yml for automated releases
• Supports both tag-triggered and manual releases
• Automatically updates version in pyproject.toml
• Generates release notes from CHANGELOG.md
• Creates GitHub releases with proper tagging

2. Version Management

• Added CHANGELOG.md following Keep a Changelog format
• Updated README.md with installation instructions for stable versions
• Added comprehensive release process documentation in docs/RELEASE_PROCESS.md
• Created scripts/release.py helper script for version management

3. User-Facing Improvements

• Users can now install specific versions: pip install git+https://github.com/perplexityai/pplx-kernels.git@v0.1.0
• Clear migration path from SHA-based installations to version tags
• Semantic versioning following semver.org specification

Benefits

1. Stability: Users can pin to stable versions instead of potentially unstable commit SHAs
2. Predictability: Semantic versioning helps users understand the impact of updates
3. Reproducibility: Version tags ensure consistent builds across environments
4. Documentation: Clear changelog and release notes for each version
5. Automation: Streamlined release process reduces manual errors

Migration Guide

Before

pip install git+https://github.com/perplexityai/pplx-kernels.git@2bd6e30fab358829bd01d1c0907be8088ff9e5e1

After

pip install git+https://github.com/perplexityai/pplx-kernels.git@v0.1.0

Release Process

1. Automated (Recommended): Use GitHub Actions workflow
2. Manual: Use the provided scripts/release.py helper script
3. Documentation: Follow docs/RELEASE_PROCESS.md for detailed instructions

Testing

• All existing functionality remains unchanged
• Installation methods are backwards compatible
• Release workflow tested with dry-run scenarios
• Version management script tested locally

Future Improvements

The foundation is now in place for:

• PyPI publishing for even easier installation
• Automated changelog generation from commit messages
• Integration with package managers
• Automated testing for each release

Resolves

• Closes Consider publishing stable tags/releases #39 - Consider publishing stable tags/releases

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Note: This PR is ready for review and testing. The first stable release (v0.1.0) can be created immediately after merging to establish the versioning baseline.