Scroll main panel by whole pages?

**Is your feature request related to a problem? Please describe.**

I'm used to using `git diff`, where I have to do f and b to scroll up/down whole pages.

I'd like to scroll up/down the main panel multiple pages in the same way for the same reason.

**Describe the solution you'd like**

I tried Ctrl-PgUp/Down and Shift-etc and they did not work. Could these be used?

**Describe alternatives you've considered**

Just dealing with it, but then I thought: why not post a feature request?

**Additional context**

Cool program everyone. Thanks for making it!