Added an NPM package for downloading, building and providing the node.js addon from source

[gkostov]

Following up on the discussion in #309 , I added this package to make it easier to build and use the node.js addon, without having to download files, run around directories and issue specific commands. Few things to highlight:

• I haven't used the WASM version but this statement in its README "The API is currently very rudimentary..." made me believe that the code is not really a 1-to-1 alternative to the node addon so it's probably best to have separate packages for each.
• I've also marked it as "1.8.3-1" to denote that it relates to the 1.8.3 version of whisper.cpp but it's good to give it a try with the "-1" version before making it a release.
• it is supposed to build fine on Windows but I could not achieve that - I guess I'm failing to setup the build environment properly

But with a proper build environment it should work as simple as

npm install whisper.cpp.node
npx whisper.cpp.node install

wait a while for the build to complete, and require("whisper.cpp.node") to start using it.

And a final question, do you find this package useful for the project or would you rather not keep it in this repo?