Add ConfigCat provider

Reasoning

I want to add an OpenFeature provider for ConfigCat.
This would be valuable because we are using that system in our projects and would like to be able to interface it with OpenFeature.
I would like to implement it and contribute the provider to this repo.

Requirements:

• generate provider via tooling
• implement Provider interface
• add tests
• complete README
• add the new provider to the OpenFeature docs

Resources

• ConfigCat

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