Allow scrolling using page up/down keys

[Mm2PL]

What should be added?

I would like for the Page Up and Page Down keys to scroll the chat window.

Why should it be added?

These keys are widely used to scroll something, like the chat window.

Reference

Comment on an older issue where I suggested this behavior, however it was not implemented with that feature.
#1533 (comment)

Mm2PL commented
Page up and page down could also be used to scroll the chat