Preset webview widths in static repls

Describe your feature request
When you’re coding HTML, it’s nice to be able to scale the screen. And you can. But. What if you could select some preset screen widths (phone, tablet, computer) or even have a list of devices to choose from?
What problem(s) would this feature solve?
Eyeballing aspect ratios is fine, but this would be so much easier, accurate and quick.
Explain what you were trying to do when you came across the problem leading to this feature request
I was working on a responsive website, and I spent some time trying to scale my webview correctly.