add default values to callbacks to prevent unnecessary warnings

Author: LonelyCpp

src/YoutubeIframe.js

@@ -18,16 +18,16 @@ const YoutubeIframe = (
     width,
     videoId,
     playList,
-    playListStartIndex,
+    playListStartIndex = 0,
     play = false,
-    onChangeState,
-    onReady,
-    onError,
-    onPlaybackQualityChange,
+    onChangeState = _event => {},
+    onReady = _event => {},
+    onError = _err => {},
+    onPlaybackQualityChange = _quality => {},
     mute = false,
     volume = 100,
     playbackRate = 1,
-    onPlaybackRateChange,
+    onPlaybackRateChange = _playbackRate => {},
     initialPlayerParams = {},
     webViewStyle,
   },