Add customized scrollbar styles

[ramith-kulal]

Description:

This pull request implements customized scrollbar styles to enhance the user experience on the website. The default browser scrollbar is replaced with a customized scrollbar that aligns better with the website's design aesthetics.

Changes Made:

• Added CSS styles to customize the scrollbar appearance.
• Utilized a blue color palette consistent with the website's design.
• Tested across different browsers and devices to ensure compatibility and accessibility.

Screenshot:

Issue Resolved: fixes #12

This contribution is made as part of GSSoC'24.