feature: support for Google Assistant API v1alpha2

[ItsWendell]

• Added support for Google Assistant API v1alpha2
• Added example for text conversations
• Changed some names of events based on new v1alpha2
• Added support for Actions
• Disabled Audio Converter (best to be done in project itself)

This solved many of the issues that I've had with this and other libraries, I have a working Electron Google Assistant client now that runs on this version, I'll release that client here on github this week.

[awernick]

Hey @WMisiedjan ! Looks good 👍 I went over the changes and I don't see anything that caught my attention. I'll test it in the next couple of days to make sure that it works on my end.

Btw. Did you do something to fix the gRPC Unavailable errors? I couldn't see anything to handle them, so my best guess is that Google improved the reliability of the service with v1alpha2.

[ItsWendell]

@awernick I noticed that I get grpc service unavailable error's mostly when my input audio wasn't converted properly to match the prefered format of Google. I build a function here which converts the audio to 16000hz PCM, this might be a good thing to have within the library itself;

https://github.com/WMisiedjan/google-assistant-desktop-client/blob/develop/src/renderer/assistant/microphone.js

[awernick]

@WMisiedjan Awesome! I haven't gotten around to merging your changes. From what I see everything seems great, but I just need to test it on my end before I merge it. I'll definitely do this in the next couple of days.