[Miniflare] mf.dispose() should internally await mf.ready

[RamIdeas]

Calling mf.dispose() before the mf.ready promise has resolved causes this error:

Uncaught AssertionError [ERR_ASSERTION]: false == true
    at #waitForReady (.../node_modules/miniflare/dist/src/index.js:9402:33)
    at async Miniflare.dispose (.../node_modules/miniflare/dist/src/index.js:9463:7) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: false,
  expected: true,
  operator: '=='
}

Repro:

const mf = new miniflare.Miniflare({
  name: 'my-worker',
  modules: true,
  script: 'export default { fetch: req => new Response(req.url) }'
});

await mf.dispose();

Workaround:

const mf = new miniflare.Miniflare({
  name: 'my-worker',
  modules: true,
  script: 'export default { fetch: req => new Response(req.url) }'
});

await mf.ready;
await mf.dispose();

Ideally, the dispose method would internally await the ready promise

[RamIdeas]

This is essentially fixed in cloudflare/miniflare#705 but I noticed my workaround to await mf.ready before await mf.dispose() stopped working. It seems like the ready promise returned before calling dispose never completes – I imagine it should reject?