feat: Add message validation utility for chat input (#15)

[HRISHIKESH-hackoff]

This utility provides functions to validate chat messages, check character limits, and manage user feedback.

Description

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🧹 Code refactoring (no functional changes)
• ⚡ Performance improvement
• ✅ Test improvement
• 🔧 Build or CI/CD configuration changes

How Has This Been Tested?

Screenshots

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Additional Information

Learning Outcomes

[ayushHardeniya]

Thanks for opening the PR and linking it to the issue. We appreciate the initiative.

For future contributions, please wait for maintainer confirmation or assignment on the issue before starting implementation. It helps avoid duplicate work and ensures alignment with the project approach.

We’ll review this PR and continue from here.

[ayushHardeniya]

@HRISHIKESH-hackoff, kindly update the description of your PR, by explaining properly you're implementing and how it's useful.