docs: add post-setup verification step

[Mohit-001-hash]

Description of Changes

Added a verification step to the Quick Start section of the README. The new note instructs users to send a simple test message after linking WhatsApp to confirm that Chat Buddy has been configured correctly and is responding as expected. This improves the onboarding experience by providing a clear post-setup validation step.

Related Issue Number

Fixes #None (documentation improvement)

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
• Refactor or other maintenance

How Was This Tested?

• Reviewed the updated README to ensure the verification step is placed immediately after the WhatsApp linking instructions.
• Confirmed that the added guidance aligns with the documented setup workflow and requires no changes to application behavior.

Checklist

• The code builds without errors (npm run build).
• Existing tests pass (npm test).
• New tests have been added if needed.
• Documentation has been updated to reflect these changes if needed.