docs: document ZeroVer release policy (#32)

Author: shinaji

CONTRIBUTING.md

@@ -0,0 +1,10 @@
+# Contributing
+
+## Release Policy
+
+This project uses ZeroVer with the `0.Y.Z` format.
+
+- The first PyPI release is `0.1.0`.
+- Increment `Y` for breaking changes to existing public API or CLI behavior, or for large feature changes that require users to update existing integrations or workflows.
+- Increment `Z` for backward-compatible features, including new public API or CLI additions, bug fixes, and small improvements that do not require users to change existing integrations.
+- Do not cut a release for documentation-only changes, or for internal-only changes that do not affect runtime behavior, public APIs, CLI behavior, packaging, or supported environments, unless those changes need to be published together with another releasable change.