Default value for priority doesn't get applied

[IboKhaled]

According to the documentation, when priority is left undefined, it should default to 0. However this doesn't seem to be the case.
Instead, the promises seem to be executed in a random order (not the order they were inserted into the queue in!).
When manually setting the priority to 0, the queue behaves as expected.

Example code:

import PQueue from "p-queue";

function delay(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

function addToQueue(name: string, priority?: number) {
  console.log(`adding ${name} to queue`);
  return queue.add(
    async () => {
      await delay(1000);
      console.log(`finished ${name}`);
      return Promise.resolve();
    },
    { priority }
  );
}

const queue = new PQueue({ concurrency: 1 });
const first = addToQueue("first");
const second = addToQueue("second");
const priority = addToQueue("priority", 1);
const third = addToQueue("third");

Example output	Expected output
adding first to queue	adding first to queue
adding second to queue	adding second to queue
adding priority to queue	adding priority to queue
adding third to queue	adding third to queue
finished first	finished first
finished third	finished priority
finished priority	finished second
finished second	finished third