[Code Improvement]: Use @use instead of @import in scss files

Sass writes on their [website](https://sass-lang.com/documentation/at-rules/import):
> The Sass team discourages the continued use of the @import rule. Sass will [gradually phase it out](https://github.com/sass/sass/blob/master/accepted/module-system.md#timeline) over the next few years, and eventually remove it from the language entirely. Prefer the [@use rule](https://sass-lang.com/documentation/at-rules/use) instead. (Note that only Dart Sass currently supports @use. Users of other implementations must use the @import rule instead.)