Update browser tap to async

[inancgumus]

What?

Updates the browser module's Tap methods to async.

We're putting this change into the main-browser-async branch because we're still discussing our options for migrating the K6 browser from sync to async.

Checklist

• [x] I have used a meaningful title for the PR.
• [x] I have described the changes I've made in the "What?" section above.
• [x] I have performed a self-review of my changes.
• [x] I have run the npm start command locally and verified that the changes look good.

• [x] I have made my changes in the docs/sources/next folder of the documentation.

Related PR(s)/Issue(s)

Updates https://github.com/grafana/xk6-browser/issues/1251

[inancgumus]

@ankur22

I think it's worth also adding the tap docs for the touchscreen class. I've been adding missing docs whenever I've worked on an API that requires them e.g. frame.isVisible.

👍 I thought about this, but to keep the PR focused, I preferred to update only the existing documentation for sync to async for Tap. I've added this as a task in the issue, and we can do it in the next PR.