Add Xquik API source example

[kriptoburak]

Summary

• Adds an API_SOURCES JSON example for Xquik's hosted OpenAPI document.
• Keeps the example credential-free because the OpenAPI document is public.

Validation

• Confirmed https://xquik.com/openapi.json returns OpenAPI 3.1.0 with 95 paths, server https://xquik.com, and apiKey header x-api-key.
• Ran jq against example/xquik-api-sources.json.
• Ran pnpm install with the frozen lockfile.
• Ran pnpm run build.
• Ran pnpm test. 12 tests passed.
• Ran git diff whitespace check.

Duplicate Checks

• Checked repository content for Xquik, x-twitter-scraper, xquik.com, and x-api-key before editing.
• Checked all-state PRs and issues for matching Xquik work.

[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.