docs: add README, CONTRIBUTING, and LICENCE

- Add project overview, installation, and usage guide
- Add contributing guidelines with setup and PR process
- Add MIT licence

CONTRIBUTING.md

@@ -0,0 +1,29 @@
+# Contributing
+
+## Setup
+
+```bash
+git clone https://onixbyte.dev/onixbyte/claude-code-skill-manager.git
+cd claude-code-skill-manager
+cargo build
+```
+
+## Before submitting
+
+- Run `cargo fmt` to format your code
+- Run `cargo clippy` and fix any warnings
+- Ensure `cargo build` succeeds
+
+## Pull requests
+
+- Keep changes focused and atomic
+- Write clear commit messages following the [conventional commits](https://www.conventionalcommits.org/) format
+- Open PRs against the `main` branch
+
+## Issues
+
+Bug reports and feature requests are welcome. Please include steps to reproduce when reporting bugs.
+
+## Licence
+
+By contributing, you agree that your contributions will be licensed under the [MIT Licence](LICENCE).