Add Xquik plugin

[kriptoburak]

Summary

• Add an Xquik Claude plugin with one workflow skill for X/Twitter data tasks.
• Register the plugin in the marketplace manifest and README plugin table.
• Update the README skill total and installation list.

Validation

• Checked the target tree, PRs, and issues for existing Xquik entries before pushing.
• Parsed the marketplace and plugin manifests as JSON.
• Verified README plugin and skill counts.
• Ran Git whitespace checks.
• Scanned the public diff for credentials, private implementation wording, badges, and unsupported claims.
• Checked referenced Xquik public links returned HTTP 200.

[kriptoburak]

If this is useful and you merge it after checks pass, feel free to share the PR on X/Twitter and mention my handle, burakbayir. I can repost or retweet it to my 24k followers of developers and power users, which may help more relevant users discover this repo.