Fix handling of @charset in media imports

[RyanZim]

Fixes #448

[mesineni]

When this fix is available ? which version ?

[RyanZim]

v14.0.1

[jobi-codework]

I got an issue when upgrading from v8 to v12 and the issue is that i cannot use the custom theme

./src/styles.scss - Error: Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ModuleBuildError: Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: expected "(".
╷
1254 │ @function mat.get-contrast-color-from-palette($palette, $hue) {
│ ^