Add support/UI for handheld PC platforms (Steam Deck, OneX, etc.)

Discord is already in Valve's Steam Deck's Steam OS, and it works beautifully!

However, the navigation can be cumbersome with the touchpad, switching accounts and exiting the application (which as of now must be done by 'Exit Game' menu on SteamOS) is not ideal and Discord's PC UI is not designed for smaller screens.

This request would be to provide full or just better support for Steam Deck and other handheld PC platforms such as Ayaneo Air, Logitech G Cloud, OneX Player, etc.

• Gaming UI (larger fonts, icons, maybe based on the mobile one on Android/iOS)
• Joystick-based navigation support
• Easier switching accounts, better profile management or specifying the account from the command-line (so that a shortcut for an specific account can be created and added to SteamOS UI or equivalent).
• Some way to exit the application without having to kill it (hurts me more than you)