TBC: Spike: Can we use CSS variables by importing the files into React

[danhalson]

In projects we're able to import css variables (exported from the scss: https://github.com/RaspberryPiFoundation/projects-ui/blob/issue-2083-Redesign_and_rebuild_homepage/src/assets/stylesheets/rpf_design_system/_colours.scss), check if this possible on editor without any webpack tweaks, and make any changes to existing files to support it (i.e. add the exports).

This is only relevant for new variables if we decide to do #555 and #556 and #557

[create-issue-branch]

Branch issues/558-Spike_Can_we_use_CSS_variables_by_importing_the_files_into_React created!