Remove build warnings

[MicrowaveDev]

DEPRECATION WARNING: Using / for division is deprecated and will be removed in Dart Sass 2.0.0.

Recommendation: math.div(20em, 16)

More info and automated migrator: https://sass-lang.com/d/slash-div

╷ 12 │ $fa-fw-width: (20em / 16); │ ^^^^^^^^^ ╵ node_modules/font-awesome/scss/_variables.scss 12:25 @import node_modules/font-awesome/scss/solid.scss 5:9 @import src/styles/main.scss 13:9 root stylesheet

[MicrowaveDev]

https://github.com/FortAwesome/Font-Awesome/issues/17946