Using css variables in style declarations are always converted to kebab-case

[itsdouges]

Describe the bug

When writing css variables that aren't kebab case, for example camelCase or snake_case, Compiled ends up transforming it to kebab-case.

To Reproduce

const styles = cssMap({
  '--helloWorld': 'red',
});

The output css variable is --hello-world.

Expected behavior

--helloWorld: red; stays as --helloWorld: red;.

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.