Draft: Add new transcriber plugin using Vosk API

I would like to move this Vosk transcriber plugin upstream so we can get better visibility and keep it up to date. Let me know if this is good.

I added the plugin to the sub-folder "net". But I would like to implement in the future another element using Vosk as a library. Maybe using this bindings, but not sure when I would to that as the bindings seem to be a bit complicated to compile today. Just highlighting this here, since might then not be a great idea then to have this plugin under "net". But we can think about this whenever this becomes a possible problem. 😄