Register a speech synthesis voice.
| aService | the service that provides this voice. |
| aUri | a unique identifier for this voice. |
| aName | human-readable name for this voice. |
| aLang | a BCP 47 language tag. |
| aLocalService | true if service does not require network. |
Remove a speech synthesis voice.
| aService | the service that was used to add the voice. |
| aUri | a unique identifier of an existing voice. |
Set a voice as default.
| aUri | a unique identifier of an existing voice. |
| aIsDefault | true if this voice should be toggled as default. |