Add support get voice list in lib

[attila-lin]

Hello~

It is not support in lib but in bin.

And we may make the options better in lib.

For example, make the enum value locale and Role iter/to_stringable (with strum crate)

[kxxt]

Landed in v5.2.0.

For example, make the enum value locale and Role iter/to_stringable (with strum crate)

I will make some improvements later. (Note that the locale is just a string, not an enum).