Add Xquik X/Twitter scraper plugin

[kriptoburak]

Summary

• add the existing Xquik plugin bundle to the external marketplace catalog
• point the catalog entry to its versioned, MIT-licensed source repository
• document the plugin alongside the other externally hosted plugins

Why

GitHub Copilot CLI now warns that direct repository installs are deprecated in favor of marketplace installs. The existing Xquik bundle already provides a Copilot-compatible plugin manifest, hosted MCP configuration, and two Agent Skills. This entry makes the supported plugin@marketplace installation path available without duplicating the plugin source in this repository.

Validation

• GitHub Copilot CLI v1.0.80 browsed the modified marketplace and found x-twitter-scraper
• copilot plugin install x-twitter-scraper@<local-marketplace> completed successfully
• copilot plugin list reported x-twitter-scraper v2.6.5 and the installer discovered 2 skills
• source package: 34 tests pass; reproducibility and version checks pass; npm audit reports 0 vulnerabilities
• marketplace JSON parses cleanly, contains unique plugin names, and matches the source manifest version and license
• linked repository, documentation, website, and OAuth discovery endpoints return successfully