SOLCjs to use webworker

[ninabreznik]

• fix solcjs compiler to use webworker

[alincode]

https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers

[alincode]

https://github.com/ethereum-play/editor-solidity/blob/master/src/editor-solidity.js#L63

https://www.youtube.com/watch?v=HcSqj1apNHI

[serapath]

Currently we have 1 module (solc-js) and we need is 2 more modules:

1. solc-js-webworker (which does require('solc-js'))
   • and it get's loaded in a web worker
   • listens to messages like:

       onmessage = event => {
         const [msgID, from, path, ref, type, body] = event.data
       }

   • and it receives messages and calls solc-js methods
2. solc-js-proxy
   • it loads a web worker with solc-js-webworker
   • it offers the same methods as solc-js
   • it forwards method calls to the webworker

       solcjs_worker.postMessage([msgID, from, path, ref, type, body])

   • it listens for responses from the webworker

       solcjs_worker.onmessage = event => {
         const [msgID, from, path, ref, type, body] = event.data
       }

   • it responds to the original method call with the result, so solc-js methods need to be async/await