Creates a new text to speech channel where text to speech requests are fulfilled by a user implemented C++ text to speech class. If you have not specified a custom text to speech class to be used, use AddDefaultChannel instead. This will not add a channel if the channel Id is not unique or if the user has not specified a custom text to speech class to be used in ITextToSpeechModule. Newly added channels must be activated to use text to speech functionalities.