[graphiql] CSS map file missing from package

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Current Behavior

The bottom of the `graphiql.css` file mentions a source mapping URL as follows:

```
/*# sourceMappingURL=graphiql.css.map*/
```

But this file is not included in the module - this throws warnings with a standard vite build workflow.

This is in version `3.8.3`.

### Expected Behavior

This file to exist, and no missing map file warnings to be present.

### Steps To Reproduce

Build a project with graphiql with aforementioned version w Vite.

### Environment

* GraphiQL Version: 3.8.3

### Anything else?

_No response_