Create page for k6/browser ElementHandle|Frame|Page|Locator's setChecked methods

[heitortsergent]

Related to #1664.

The docs are missing a page for the setChecked function for the ElementHandle object.

[heitortsergent]

@inancgumus @ankur22 we got some feedback that we had a 404 on the ElementHandle page and I think we're just missing a page for one of the functions here. I removed the link for now, would you be able to grab this issue? 🙇

[inancgumus]

It turns out that we don't publish ElementHandle.setChecked to users (it's not available on the browser module's Javascript API). Instead, we have ElementHandle.check and ElementHandle.uncheck. The difference of setChecked is that it toggles input checkboxes.

Next steps:

• Publish setChecked to users
• Update the documentation

[inancgumus]

@heitortsergent This can be closed once the reviewers approve #1696 🎉

We made all the necessary updates in grafana/xk6-browser#1340.