Migrate from Custom Scrollbar Styles to Native Scrollbars with dark mode support and thin CSS Property

[hichemfantar]

Currently, the expo project websites use custom scrollbar styles, which often lead to inconsistent appearance and behavior across different browsers. This impacts both the visual consistency and user experience, particularly in browsers with limited support for custom scrollbars like firefox and safari.

To address this, I propose switching to native browser scrollbars which are dark mode compatible and utilizing the CSS thin property to maintain a minimal and elegant design. This approach ensures better cross-browser compatibility and reduces maintenance complexity.

thin property: https://developer.mozilla.org/en-US/docs/Web/CSS/scrollbar-width#thin

this pr implements dark mode support for native scrollbars

chrome existing styles:

chrome with native scrollbar:

chrome with native scrollbar and thin property:

firefox existing styles:

firefox existing styles with thin property: