Added custom scrollbar for Firefox

[Alenjojo]

Description

• Added syntax in css which will affect the scrollbar of firefox.There were some limits for firefox but i tried my best
• Fixes #237

Affected Dependencies

NA

How has this been tested?

In firefox browser

GIF Before

• If any UI Changes, Use this to record or else specify NA

  GIF After

  

Checklist

• [X] I have followed the Contribution Guidelines.
• [X] My changes do not edit/add any unrequired files.
• [X] My changes are covered by tests.

[Alenjojo]

And btw shouldn't be fixing errors or small fixes be level2. Just asking

[Praful932]

@Alenjojo Why did you close the PR? You can push commits into this one only no