Adding support for "additionalData"

[leifniem]

While working on our design system i ran into the issue that we use the additionalData option present in Vite and Webpack's scss-loader to add global preambles for importing our SCSS variables and the Sass libraries for math, lists, etc.

This is probably a use case for a custom resolver, but i wanted to check if this is probably an option that should be available to the cli.

Thanks for this project, it's very promising!

[mizdra]

--additionalData option is currently not supported.

This is a feature missing from happy-css-modules. I think that it would be worth implementing 👍.