Dictate DispatchQueue Choice at Init

[kyledotmp3]

Was trying to use this in a server-side swift project but unfortunately we don't have an option with Swifter right now to dictate which thread is being used...

Right now it's hardcoded to .main:

DispatchQueue.main.async {
  let session = URLSession(configuration: .default, delegate: self, delegateQueue: .main)
  self.dataTask = session.dataTask(with: self.request!)
  self.dataTask?.resume()
            
  #if os(iOS)
  UIApplication.shared.isNetworkActivityIndicatorVisible = true
  #endif
}

I promise we init Swifter with the ability to choose which DispatchQueue is used

[meteochu]

I guess this was just always the case since Matt wrote the original Swifter 6 years ago (wow! 6). I don't see why we can't change it to allow for different queues. Feel free to put up a PR