Add Xquik search client

[kriptoburak]

Summary

• Adds XquikSearchClient and xquikTweetToTweet as optional helpers for API-backed tweet search.
• Returns the existing Tweet shape and leaves current scraper behavior unchanged.
• Requires an explicit API key from the caller.

Validation

• Prettier check passed.
• TypeScript no emit check passed.
• Package build passed.
• Targeted Jest and an existing test both fail before execution in this local setup with the same ESM harness error: exports is not defined.