Add Xquik skill

[kriptoburak]

Summary

• Add an installable Xquik skill for public X data research.
• Index it under the General Agent Skills section.
• Fix three adjacent awesome-list description lint items in README.

Validation

• Checked memory, target tree, and all-state PRs/issues for duplicate Xquik work.
• Ran npx --yes markdownlint-cli2 README.md skills/xquik/SKILL.md.
• Ran npx --yes awesome-lint before push.
• Post-push local awesome-lint only reports fork GitHub topic metadata.
• Ran staged diff check and public-text safety scan.
• Verified Xquik docs and public repository links return 200.