Add support for external, cloud or self hosted, TTS services

[AxelFooley]

Is your feature request related to a problem? Please describe.
The current TTS service works well but the voice is very robotic and artificial, nowadays everyone can rent for cheap or self host more advances TTS services that offer more natural voices.

Describe the solution you'd like
I am able to configure my own TTS service, being it cloud based or self hosted, by providing the API address.

Describe alternatives you've considered
There's no alternative as we can't configure it at the moment.

Additional context
Nope