Add Zod Validation Hook

Reasoning

I want to add a hook which performs validation using Zod.

• Zod is a TypeScript-first schema based validator with static type inference
• Static types can be passed as generics to the OpenFeature resolves methods for additional type safety.

TODO:

• generate hook via tooling
• implement Hook interface
• add tests
• complete README

Keep in mind the CONTRIBUTING guidelines: https://github.com/open-feature/js-sdk-contrib/blob/main/CONTRIBUTING.md