switch to a new window tests

Good afternoon everyone,

Someone on my team was just trying to submit some new tests that require we be able to create a new window and then switch to that window. I know from the readme[1] that this is not yet supported.

I wonder if anyone has a workaround or hack they've seen for doing this, or perhaps someone is already implementing this functionality. It seems important to me...

I create an issue[2], but also wanted to send mail here in case I'm just missing something obvious.

Thanks!
-John

[1] https://github.com/web-platform-tests/wpt/blob/57f28f89273e2f75324441948fefde94dda537f1/docs/writing-tests/testdriver.md
[2] https://github.com/web-platform-tests/wpt/issues/23574