Widgets should support tiling

### Description (what happens and what I expect)

The widgets have a popout button but that's not what the button does. When I click it (on a jitsi or etherpad widget), the widgets stay put right there where they were *-- no pop out!* Instead, a separate browser window (or a tab if the browser's already open) appears with the jitsi (or etherpad). This is really annoying because I set up different workspaces (I use i3wm) for different types of tasks; so it happens that my browser is sitting three workspaces down, which is very unwieldy. The first time it happened, it was only after the videoconference was over that I found out four of five jitsi widget tabs in my browser...

I consider this to be a bug, not a request for functionality. And I don't get it. Why can't the little boxes just pop out so that one can move them around as they please? That would make a big difference, specially in the case of a tiling window manager (whose users, specially those with small screens, tend to make the best out of the screen real estate).

### Steps to reproduce

Just enter a group with a widget and hit the Popout button.

### Version information

#### Platform:
* Debian Buster (up-to-date)
* Linux image 5.5.0-2-amd64
* i3 4.17.1-1
* riot-desktop 1.6.0