Move shared thread to NSQualityOfServiceUserInitiated (#651)

Co-authored-by: Sam Siner <sam.siner@ninjarmm.com>

Author: samsiner

SocketRocket/Internal/RunLoop/SRRunLoopThread.m

@@ -29,6 +29,7 @@ + (instancetype)sharedThread
     dispatch_once(&onceToken, ^{
         thread = [[SRRunLoopThread alloc] init];
         thread.name = @"com.facebook.SocketRocket.NetworkThread";
+        thread.qualityOfService = NSQualityOfServiceUserInitiated;
         [thread start];
     });
     return thread;