Bind page-up, page-down and space keys

[peterjc]

I was surprised this wasn't already done. Tested locally via a config file:

❯ serie --version
serie 0.4.2

❯ more  ~/.config/serie/config.toml
[keybind]
page_up = ["ctrl-b", "pageup"]
page_down = ["ctrl-f", "pagedown", "space"]

These controls follow the precedent of pagers like less and more and the default git log behaviour.

[lusingander]

https://github.com/lusingander/serie/releases/tag/v0.4.3