支持centerStageEnabled

Example/SellyCloudSDK/Live/SCLivePusherViewController.m

@@ -426,6 +426,7 @@
     else {
         self.livePusher = [[SellyLiveVideoPusher alloc] initWithLiveMode:SellyLiveMode_RTMP];
     }
+    self.livePusher.centerStageEnabled = true;
     self.livePusher.preview = self.liveView;
     self.livePusher.delegate = self;
     self.livePusher.enableCustomVideoProcess = true;