prettybat can't read from pipe

When trying to preview a remote file (e.g. an installer shell script) I'd like to be able to fetch a file from a server with curl and pipe the result to prettybat. This works fine when using just bat for the syntax highlighting, but prettybat either doesn't seem to support that use case or needs to be fixed.

```bash
$ curl https://sh.rustup.rs | prettybat
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0[prettybat error]: -: No such file or directory
85 18636 85 15971 0 0 318k 0 --:--:-- --:--:-- --:--:-- 318k
curl: (23) Failure writing output to destination
```

It would be nice if this could be supported.