Suggestion to accept list of streams as an argument

Hello. I am wondering - why isn't there an option to directly reference streams array in the constructor?

So intead of
```
const combinedStream = new CombinedStream();

readStreams.forEach((readStream) => {
combinedStream.append(readStream);
});
```

I could use
```
const combinedStream = new CombinedStream({ streams: readStreams });
```

Seems like a nice feature to have