feat: keyboard shortcut navigation #23

I saw someone asking for a bluesky client with J/K up/down L-like R-reply keybinds, and thought those could be implemented in Witchsky web (possibly mobile too? I know android has support for keyboards, but don't know how well React Native supports it).

Could copy clipboard shortcuts from the Mastodon client Phanpy. Anisota and Wafrn also have keybinds!