How to get binary data in the beforeSendResponse callback?

Hi. I'm looking for a way to access binary data from proxied resources upstream. Please let me know if this is possible!

#### Which platform are you running AnyProxy
Linux (Ubuntu 18)

#### The version of the AnyProxy
4.1.2

#### Your expected behavior of AnyProxy
I would like to be able to access binary data in the `beforeSendResponse` function. It seems like this is currently not possible

#### The actual behavior of AnyProxy
```
const beforeSendResponse = async (requestDetail, responseDetail) => {
console.log(responseDetail.response)
}
```

This code logs the response, which is:

```
{
statusCode: 304,
header: {
'Cache-Control': 'private, must-revalidate, max-age=0',
Vary: 'Origin',
Server: 'Microsoft-IIS/10.0,',
'X-Content-Type-Options': 'nosniff',
'X-XSS-Protection': '1; mode=block',
'X-AspNet-Version': '4.0.30319',
'X-Powered-By': 'ASP.NET',
Date: 'Fri, 17 Apr 2020 06:10:21 GMT',
Connection: 'close',
'x-anyproxy-origin-content-length': 0
},
body: ,
rawBody: []
}
```

I know that in Node.js I would do something along the lines of:

```
result = ''
res.on('data', (body) => result += body)
res.on('end', ...)
```

I understand that this is handling 'chunks' sent as a response by the upstream server? I'm not sure... I'm quite new to this.

But from what I can tell.... I simply just can't access the response body if that body is an image or other binary data.

Surely there is a way??

Start at the beforeSendResponse callback and inspect how responseDetail.response exposes body and rawBody in AnyProxy 4.1.2. Verify that binary data from upstream resources is available to the callback without corruption; the payload names no file or test to run.

Written by the indexing model from the issue text.