Allow TTS notifications to also show as normal notifications

**Is your feature request related to a problem? Please describe.**
When using Text-to-speech (TTS) notifications, only the voice is played, no actual notification is displayed

**Describe the solution you'd like**
I would like an option to also use the normal behavior (with all the nice features we have, such as url, image, ecc...) with TTS notifications.
Ideally, the app should not check for the _message_ being _TTS_. If the _tts_text_ data attribute is set, just speak the given message. To still allow voice-only notifications a new _message_ HIDDEN (or something like that) could be used.

**Describe alternatives you've considered, if any**
Use two notifications, one for TTS and one for text. But this would mean two notifications used against the 500 rate limit and general greater general overhead for the server and the phone.

**Additional context**
I have tested on Android