Add examples and test materials for new policy development CLI tools

[danlishka]

Goal

Make it easy for developers to understand the new policy development CLI tools in 15 minutes with working examples they can copy, modify, an test locally.

Creating a new docs/examples/policies/quickstart/ directory with examples and test materials for the new chainloop policy develop CLI tools.

Policy Examples:

• SBOM freshness checking policy

Test Materials:

• Sample files for each policy type
• Clear passing/failing test cases for chainloop policy develop eval

Documentation:

• Step-by-step quickstart guide
• Policy development best practices

CLI Tools Context

The new policy development CLI provides (CLI docs):

• chainloop policy develop init - Initialize policy templates
• chainloop policy develop lint - Validate policy structure and Rego syntax
• chainloop policy develop eval - Test policies against materials locally