fix: extract correct author name in content script

[tuliosousapro]

Updates the author extraction logic in source/chrome/contentScript.js to avoid incorrectly capturing the "Your Kindle Notes For:" prefix paragraph. This brings the logic in line with the fix already implemented in batchExport.js. A new test case is added under tests/ using jest and jsdom to verify the DOM querying logic works as expected.

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PR created automatically by Jules for task 6415276485350050814 started by @tuliosousapro

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Code Review

This pull request introduces a testing suite using Jest and JSDOM, including a configuration file and a new test for author extraction. The core logic in contentScript.js is updated to improve author detection by targeting specific metadata elements. Review feedback highlights that the specified dependency versions in package.json are likely invalid and suggests a fallback for the author extraction logic to prevent empty strings when metadata is present but blank.