Fix importing the worker thread file

[derhuerst]

Before it would fail if you use crypto-hash with Node 12 (or anything with worker_threads rather). The tests didn't fail because they run with $PWD pointing to the repo.

const {sha512} = require('crypto-hash')
sha512('foo').then(console.log, console.error)

[Error: Cannot find module '/Users/j/playground/thread.js'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:623:15)
    at Function.Module._load (internal/modules/cjs/loader.js:527:27)
    at Function.Module.runMain (internal/modules/cjs/loader.js:837:10)
    at MessagePort.<anonymous> (internal/main/worker_thread.js:139:25)
    at MessagePort.emit (events.js:200:13)
    at MessagePort.onmessage (internal/worker/io.js:70:8) {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}] {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}

One way to test this might be to move test.js to test/index.js and then run cd test; ava index.js.

[sindresorhus]

Thanks for catching this :)