`typst.compile` type hint issue

Nobody has claimed this yet.

Thank you for creating this awesome package!

I was having some issues with type hints on `typst.compile`:

```
def compile(
input: Input,
output: Optional[Input] = None,
root: Optional[Input] = None,
font_paths: Union[Fonts, List[Input]] = [],
ignore_system_fonts: bool = False,
format: Optional[OutputFormat] = None,
ppi: Optional[float] = None,
sys_inputs: Dict[str, str] = {},
pdf_standards: PDFStandards = [],
package_path: Optional[PathLike] = None,
timestamp: Optional[CreationTimestamp] = None,
pretty: bool = False,
package_cache_path: Optional[PathLike] = None,
) -> Optional[Union[bytes, List[bytes]]]:
```

1. Perhaps `root` shall be `Optional[PathLike]` rather than `Optional[Input]`?
2. `Input` defined with `TypeVar`, which blocks us to use a `bytes` input with a `str` output. (I'm not sure if this was intentional.)

Start from the type annotations for `typst.compile` and inspect how `root`, `Input`, and the input/output relationship are defined. Verify the intended accepted combinations with a type checker, then update the annotations so the documented path and byte/string combinations are represented accurately.

Written by the indexing model from the issue text.