Add support for WebWorker with worker-plugin

[Krivega]

Closes #3660

I used to test a simple example of the test plugin

// index.js

const worker = new Worker('./worker', { type: 'module' });

worker.onmessage = ({ data }) => {
  console.log('page got data: ', data);
};

worker.postMessage('hello');

// worker.js

import { foo } from './dep';

console.log('hello from worker');

addEventListener('message', ({ data }) => {
  console.log('worker got message', data);

  if (data === 'hello') {
    postMessage(foo);
  }
});

// deep.js

export const foo = 'bar';

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at [email protected]. Thanks!

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[iansu]

There is an existing PR that's very similar here: #3934

In the thread for #3660 there were some issued raised about browser compatibility with worker-plugin which I think need to be investigated.

[Krivega]

@iasu right, I'll try to fix it in the plugin and then try again