Find a way to specify options for the syntax

We may want to support names other than `css`, for example if someone names theirs `style` or something:

```ts
style`.foo { color: blue; }`;
```

not entirely sure if there's a way to pass options to a postcss custom syntax, though. needs investigation

Look at the PostCSS custom syntax API to see if options can be passed. Check the existing syntax implementation in the source code, likely in a file like src/syntax.ts. Investigate how the current tag name 'css' is detected and whether it can be made configurable. Determine what changes are needed to allow users to specify custom tag names like 'style'.

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