Add support for inline snapshots tests

What is the problem this feature will solve?

Jest inline shapshots are like file-based snapshots but much more casual. I love using them for small snapshots and I think they'd be a great improvement to Node.js. From Jest's docs, they look like:

it('renders correctly', () => {
  const tree = renderer
    .create(<Link page="https://example.com">Example Site</Link>)
    .toJSON();
  expect(tree).toMatchInlineSnapshot(`
<a
  className="normal"
  href="https://example.com"
  onMouseEnter={[Function]}
  onMouseLeave={[Function]}
>
  Example Site
</a>
`);
});

What is the feature you are proposing to solve the problem?

The Node.js version might look like:

test("renders correctly", async ctx => {
  const tree = renderer
    .create(<Link page="https://example.com">Example Site</Link>)
    .toJSON();
  ctx.assert.snapshotInline(`
<a
  className="normal"
  href="https://example.com"
  onMouseEnter={[Function]}
  onMouseLeave={[Function]}
>
  Example Site
</a>
`);
});

What alternatives have you considered?

I use file snapshots or assert.deepEqual().

Inizia dalla documentazione di Jest inline snapshots collegata nell’issue e confrontala con la API di test proposta di Node.js, ctx.assert.snapshotInline. Esamina le alternative esistenti file-snapshot e assert.deepEqual; il lavoro è completo quando Node.js supporta il flusso di test inline-snapshot proposto descritto nell’esempio.