When using the iOS ReplayKit to broadcast video feed, the audio of the microphone is not available/broadcasted.

To repro:
1: Open attached project
2: Build for iOS
3: Adding following to Xcode info.plist:

<key>NSCameraUsageDescription</key>
<string>Front-facing camera during gameplay</string>
<key>NSMicrophoneUsageDescription</key>
<string>Record microphone for commentary</string>

4: Run on iOS 10 device (tested iPhone SE iOS 10.0.2) with Mobcrush app installed
5: Accept permissions for camera and microphone
6: Click Start Broadcast button
7: Broadcast to Mobcrush
8: Open up broadcasting on webpage (on a computer)
9: See that there is no sound being broadcast from the microphone