Allow the User to change the eSpeak-NG voice used

**Is your feature request related to a problem? Please describe.**
Adding an entry for Speech Dispatcher to allow the user to enable a voice variant.

**Describe the solution you'd like**
Something like "EspeakVoice" in espeak-ng.conf would be nice to have...

**Describe alternatives you've considered**
~~A clear and concise description of any alternative solutions or features you've considered.~~

**Additional context**
~~Add any other context about the feature request here.~~