Add Support For Mozila Deep Speech

[pedrooaugusto]

Description

Mozila Deep Speech is maybe the most popular open source and free to use speech-to-text engine out there. This project already supports 3 different speech-to-text providers: Azure, Google and Chrome, but just one of them, webkitSpeechRecognition (Chrome), is free and even then it only works in the browser, meaning that it does not work inside an Electron app.

Mozila Deep Speech in the other hand, is free and works in almost every device, we can even ship it alongside an electron app. The only drawback of Deep Speech is that it lacks support for other languages (mainly portuguese), but even then it can be trained to do so.

The aim of this issue is to add support for Deep Speech as a new speech-to-text provider.