Feature request: Scroll in active channel using keyboard

[bendoin]

Couldn't find a feature lite this in any issues, but feel free to close out if need be.

As a user I want to be able to scroll through the text in the active channel using page up and page down. Might also be good be able to scroll one line at a time using the arrow keys potentially, but that would be secondary.

Bonus points (or separate issue I guess) is if tab and shift + tab cycles through the channels that are open for more keyboard friendly reading.