Improved settings handling and theme update logic in js/src/index.tsx

[prashantzsingh]

• I've extracted the logic for determining column settings into a separate function updateColumnsFromSettings. This reduces redundancy and improves maintainability.
• I've replaced static icon update methods with a dynamic, reactive useEffect hook to automatically adjust the styles whenever the theme changes. This ensures that the icons always match the current theme without manually refreshing them.
• I've included comments to describe the purpose and impact of each change. This will help other developers understand the intent behind the changes and make further modifications more effectively.

[github-actions]

Launch a binder notebook on branch prashantzsingh/jupyter-fs/update-docs