[Enhancement] Navigate between pages on the left by pressing Up/Down, without having to press A to switch pages

[ghost]

In official Nintendo menus (including the original user page), the UI will switch between pages just by pressing Up/Down, it doesn't need you to press A. So in the spirit of trying to make this app feel as close as possible like the official menus, I think it should be changed to where you can navigate between Recent Activity, All Activity, and Settings, just by pressing Up/Down in the sidebar, without needing an additional A press.

(Continuation of #40)