User guide for node use

1. Install @ricky0123/vad-node:

   npm i @ricky0123/vad-node

   No other setup is necessary.

2. Example usage:

   const vad = require("@ricky0123/vad-node")
   
   const options: Partial<vad.NonRealTimeVADOptions> = { /* ... */ }
   const myvad = await vad.NonRealTimeVAD.new(options)
   const audioFileData, nativeSampleRate = ... // get audio and sample rate from file or something
   for await (const {audio, start, end} of myvad.run(audioFileData, nativeSampleRate)) {
      // do stuff with
      //   audio (float32array of audio)
      //   start (milliseconds into audio where speech starts)
      //   end (milliseconds into audio where speech ends)
   }

   See the docs for NonRealTimeVAD for details. That is the only currently supported API in node.