[Bug]: Latest fontsouce versions >5 does not work with variable fonts

[jsve]

Demo URL

https://github.com/fontsource/fontsource/blob/main/CHANGELOG.md#breaking-changes

What happened?

Hi,

This looks like a great project! However, when testing it out I had some issues setting it up following your guide. It turns out that the reason I was having issues is that since version 5 of fontsource, they have split variable fonts into their own packages.

Ideally this repo should be updated to handle variable fonts, but a quick fix would be to update the documentation with a warning and clear information in the example configs that version ^4 needs to be used.

Reproduction steps

1. Follow the setup guide for fontsource
2. use the template config with fontsource
3. get error messages as stated below

Relevant log output

`ENOENT: no such file or directory, open '@fontsource/cabin/variable-full.css'`

What browsers are you seeing the problem on?

No response

What is your operating system?

No response