Update example app to use CSS instead of SCSS Variables

[PKulkoRaccoonGang]

Description

Following the migration to design tokens, Paragon components have moved entirely from SCSS variables to CSS variables. The example app in version 23, however, still contains configurations that rely on SCSS-based variables.
It would be great to update these configurations and fix the styling issues in the example app.

• example/src/index.scss
• example/module.config.js