Update CONTRIBUTING.md

What does this merge request do?

Describe your changes. Examples from our project:

• Fixed TypeError in Browse page by adding proper None checks to hf_storage.py
• Replaced HTML card rendering with Streamlit native components
• Added comprehensive error handling for Hugging Face dataset loading
• Updated sidebar navigation to work consistently across all pages
• Enhanced type safety with str() conversions for all data fields

What type of change is this?

• Bug fix (like fixing the Browse page TypeError we had)
• New feature (like adding language detection or search functionality)
• UI improvement (like the sidebar redesign we did)
• Data handling fix (like the HF dataset integration issues)
• Documentation update

How did you test this?

Check what you tested:

• Ran streamlit run app.py locally and everything works
• Tested on the live Hugging Face Spaces deployment
• Checked that Browse page loads proverbs without errors
• Verified Submit page saves data to both local and HF dataset
• Tested navigation between all pages (Home, Browse, Submit, About, Contact)
• Confirmed data loads properly from the HF dataset (manish1106/desi-proverbs)

Pre-merge checklist

• Code follows our style (Black formatting, Ruff linting passes)
• No new console errors or warnings
• Tested with actual proverb data from our dataset
• Updated any documentation if needed
• Changes work with our current HF_TOKEN setup

Related issues

If this fixes a specific issue, mention it: Closes #issue_number

Notes for reviewers

Anything specific you want us to check? For example:

• Pay attention to the error handling in this function
• Test this specifically with Tamil/Hindi proverbs
• Check if this affects the HF dataset synchronization

Screenshots

If this changes how the app looks, add before/after screenshots.