Add CONTRIBUTING.md and GitHub issue/PR templates #60
Description
The project has 768 stars, 146 forks, 8 open pull requests, and uses the Claude Code Action for automated PR reviews — yet there are no issue templates, PR templates, or a CONTRIBUTING.md. This means:
- Bug reports lack the structured information (reproduction steps, environment, expected vs actual behavior) needed to triage them quickly.
- PRs don't consistently include context about what was changed and why, making automated Claude reviews less effective.
- New contributors have no guidance on code style, branch naming, commit format, or which areas of the codebase welcome contributions.