[Bug]: Fontsource loader writes wrong path

[luastoned]

Hello,

these two cases push an additional / breaking import statement.

https://github.com/cssninjaStudio/unplugin-fonts/blob/a7e66d594e2c7e0a2cccfed7c15a069ffebb96c1/src/loaders/fontsource.ts#L66-L71

The build step then breaks:

transforming (1) index.htmlUnable to resolve `@import "import '@fontsource-variable/open-sans/standard.css';"` from /undebug
✓ 4 modules transformed.
x Build failed in 84ms
error during build:
Error: [vite:css] [postcss] ENOENT: no such file or directory, open 'import '@fontsource-variable/open-sans/standard.css';'
file: unfonts.css:undefined:NaN

The logic for variable is also odd, it does not matter if opsz is true or false, simply being there has unintended side effects.