FEATURE REQUEST: Ability to control response stream

### New Issue Checklist

- [x] I have tried with the latest version of OHHTTPStubs
- [x] I have read the [README](https://github.com/AliSoftware/OHHTTPStubs/blob/master/README.md)
- [x] I have read the [Using the right Swift Version of `OHHTTPStubs` for your project](https://github.com/AliSoftware/OHHTTPStubs#using-the-right-swift-version-of-ohhttpstubs-for-your-project) section
- [x] I have searched in the [existing issues](https://github.com/AliSoftware/OHHTTPStubs/issues?utf8=✓&q=is%3Aissue)
- [x] I have read [the OHHTTPStubs wiki](https://github.com/AliSoftware/OHHTTPStubs/wiki) to see if there wasn't a detailed page talking about my issue

### Environment

- version of OHHTTPStubs: 9.1.0
- integration method you are using:
* [ ] Cocoapods
* [ ] Carthage
* [ ] submodule
* [x] other Swift Package Manager
- version of the tool you use: Uhh....package tools version 5.6

### Issue Description

I am attempting to use this to test a Server-Sent Events implementation. That particular protocol likes to send data in chunks of varying sizes as it streams, example:
```
id: 1
data: This

data: is

data: a

data: sentence

data: .
```

OHHTTPStubs at the moment doesn't seem to expose a way to send partial responses back as part of the stream. Specifically, what I need is the URLSessionDataDelegate to have its `urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data)` method called with each sent event.

An ideal solution in my mind would be to allow me to pass an array of `Data` to the response and have it work out the rest, but honestly I'd be up for anything that worked.