Support for Chrome OS natural voices

[HadrienGardeur]

In the latest Chrome OS update, Google added support for natural voices on some languages.

Based on the few tests that I've made so far, these natural voices seem to be similar to the Android voices available in Chrome OS that we already document in this repo. The main difference being that you can use these natural voices offline as well.

We could use a similar approach to what we already document with Apple voices where:

• the primary name would become these new natural voices
• but we would keep on documenting the Android voices in altNames

[HadrienGardeur]

Now that I've tested support for Dutch natural voices, I can confirm that these are equivalent to the (badly named) Android ones.

[HadrienGardeur]

Natural voices in Chrome OS only support 6 languages through vs 70+ through the embedded Android voices.