…mJSON test

Updates the `createTemplateFromJSON` unit test to include specific assertions for `new_ui_enabled`, `personalized_welcome_message`, and `experiment_enabled` parameters. This ensures that Rollout, Personalization, and Experiment value types are correctly handled when creating a template from a JSON string.

Updates the `createTemplateFromJSON` unit test to explicitly cast conditional values to `RolloutParameterValue`, `PersonalizationParameterValue`, and `ExperimentParameterValue` interfaces.
Asserts on individual fields of these values instead of generic object equality checks.
Exports the necessary interfaces from `src/remote-config/index.ts` to support these assertions.