Added corner-shape: squircle; to SourceSelector.module.css for more visually appealing rounded corners.
Customized windows source selector scrollbar to be more subtle but carry the product colour.
Removed box-shadow on SourceSelector because electron doesn't round corners of the shadow, thereby leaving a square border shadow conflicting with the rounded corners of the SourceSelector.
Introduced CSS classes to hide scrollbars while maintaining scrollability across browsers. Also removed unnecessary blank lines in frameRenderer.ts for code cleanliness.
Siddharth