Add Xquik X research skill

[kriptoburak]

Summary

• Add an xquik-x-research skill for Xquik exports, REST API responses, and MCP output.
• Add a user-facing skill README and a small scoring reference.
• Keep retrieved social content as untrusted evidence and API keys in environment variables.

Validation

• python3 scripts/validate-skills.py
• git diff --check
• Public diff scanned for non-public implementation details, credentials, and pricing details

[kriptoburak]

Optional visibility note: If this is merged and you'd like a visibility boost, feel free to share the PR or release on X/Twitter and tag x.com/burakbayir. I can repost it to my 24k followers so more developers can discover this repo.