added cheatsheet page of frontend

[deepthidornala]

📄 Description

This PR adds a new Cheat Sheet page to the DevNotes frontend. It includes concise, topic-wise summaries for:

• HTML
• CSS
• JavaScript
• React
• Tailwind CSS

Each section contains important syntax, properties, or commands, presented in a copy-friendly, structured format.
The purpose is to help learners quickly revise key concepts without scrolling through the full learning content. This feature complements the existing learning + quiz workflow and improves retention.

✅ Checklist

• My code follows the project’s coding guidelines.
• I have tested these changes locally.
• I have added necessary documentation/comments (if applicable).
• I have linked the related issue.

🔗 Related Issue

Closes #54

📸 Screenshots & video (if applicable)

🙏 Additional Notes

• UI is designed to be clean, accessible, and responsive.
• I'm open to feedback and suggestions for improvements or new sections.

Thank you for reviewing this PR!

[deepthidornala]