feat(AvatarGroup): add a new "moreTooltip" prop

[Mathu-lmn]

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This pull request adds support for customizable tooltips on the overflow (“+N”) avatar in the AvatarGroup component. It allows developers to specify either a static string or a function for the tooltip content.
Added a new section in avatar-group.md explaining how to use the more-tooltip prop and showing usage examples and updated the playground to show the new prop in use

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

Could probably get added to v4 but I couldn't find any information on the current v4 PR acceptance status