Add async check helper

[inancgumus]

What

Add a helper that supports asynchronous check functionality.

Example (currently, it does not work):

check(page, {
    'checked': async p => await p.locator('.checked').isChecked(),
});

We use the following code until we add async check support:

const isChecked = await p.locator('.checked').isChecked();
check(page, {
    'checked': p => isChecked,
});

Why

We're converting the browser's sync methods to async. We noticed that check intentionally does not allow async methods in it. This issue isn't great for user experience (also considering the browser's 150ish methods will be async). Can we find a way to make this more user-friendly?

Tasks

Beta Give feedback

1. Add async check util k6-jslib-utils#13
   +0
2. Upload the library
3. Docs: Replace sync check usage with async check k6-docs#1725
   +0
4. k6: Add it to release notes

[inancgumus]

Updating k6-docs will be tackled in another issue: grafana/k6-docs#1725