Wp-calypso: SPT: Scrolling behavior is unexpected

[shaunandrews]

Right now, the scrolling behavior when choosing a page template is confusing. The list of templates scroll with the page, while the large preview scrolls on its own.

This is backwards.

• I'd expect the list of templates to be fixed to the top/left/bottom, and scroll independent from the rest of the page.
• The large preview should scroll naturally with the page — and not be contained within a scrolling container.

[apeatling]

@shaunandrews Is it possible to get some sort of visual to explain this one? It's going to be easy to not get this right again.

[shaunandrews]

I made a quick CodePen to show what I mean:

https://cdpn.io/shaunandrews/debug/PoorBww

Here's a GIF of it in action: