JaeYun Park

Background play and sound mix not working ( setSharedInstance() not working )

1

## 🐛 Bug Report ### Expected behavior ``` dart await flutterTts.setSharedInstance(true); ``` ``` dart await flutterTts.setIosAudioCategory(IosTextToSpeechAudioCategory.ambient, [ IosTextToSpeechAudioCategoryOptions.allowBluetooth, IosTextToSpeechAudioCategoryOptions.allowBluetoothA2DP, IosTextToSpeechAudioCategoryOptions.mixWithOthers ], IosTextToSpeechAudioMode.voicePrompt ); ``` above method doesn't work ``` dart...