Custom scroll bar for the side Navbar

[Amruta7203]

Is your feature request related to a problem? Please describe.
The default scroll bar seems to decrease user experience.

Describe the solution you'd like
Customizing the scroll bar for the side Navigation bar enhances the user interface and gives better user experience.

** Add screenshot

Checklist
Example Fill x { [x] } into bracket

• [x ] I have checked the existing issues *
• [x ] I have read the Contributing Guidelines *
• [x ] I have starred the repository *
• [x ] Working under Gssoc'24

[panwar8279]

hi @Amruta7203 , i am assigning this issue to you, kindly complete within 2 days. Good Luck!