[CM-1395] Exposed the Language change code

[AbhijeetRanjan308]

Summary

• Exposed the language change code.
• To Update language just need to pass language code like this : KommunicateFlutterPlugin.updateUserLanguage("fr");
  • Expose Method to update the chat bar text fill. KommunicateFlutterPlugin.updatePrefilledText(String)
• Expose the Send Message code.

  KommunicateFlutterPlugin.sendMessage({
      'channelID' : '94588068',
      'message' : 'Hi Message sent'
    });

• Filled the gap for fetchUserDetails Function.

  To Test Prefilled

• add this function just after opening conversation function:

  void _startTimer() {
  Future.delayed(Duration(seconds: 10), () {
    KommunicateFlutterPlugin.updatePrefilledText("0000123");
    print("function of updatePrefilled is called");
  });
  }