Custom Scrollbar added

[DEEPALI-SUK]

Description

Issue FIXES #178

Describe the changes you've made

Custom Scrollbar added in the website.

Describe if there is any unusual behaviour of your code(Write NA if there isn't)

NA

Checklist

• I have added my name in the contributors list at the end of README.md file.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• The title of my pull request is a short description of the requested changes.
• Open Source Program names(OPTIONAL: If you participated in any open-source program then please mention the program name here)

[vercel]

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🔍 Inspect: https://vercel.com/feminine-devine/periodoo/51kd42KLqVjLQERoYSVSTofhRixz
✅ Preview: https://periodoo-git-fork-deepali-suk-deepali-suk-feminine-devine.vercel.app

[khushishikhu]

@DEEPALI-SUK LGTM!! 💯 Thank you for contributing. Keep it up

[DEEPALI-SUK]

@khushishikhu Kindly, add correct label for my level, there should not be space present between Level and 2, because of this my scores are not displayed in the leaderboard.
Thank you.