Flathub manifest for ROTA

• To install the app, visit Flathub
• For the game source code, issue tracking, etc. see @HarmonyHoney/ROTA

Permissions

• --socket=x11: ROTA is built with Godot Engine 3.6. Wayland support didn't come until Godot 4.3, and porting from 3.6 to 4.3 is pretty monumental; thus X11/XWayland needs to be used unless/until someone volunteers to port to Godot Engine 4.3+.

• --device=all: Necessary for controller support. See: #2