feat: add pause menu and quit function

[skleinjung]

• Memoize useDispatch result when possible.
• Add useKeyHandler hook for working with global key events.
• Add game state, with initial 'paused' property.
• Add 'pause' key handling to expedition screen.
• Increase panel font size to enhance readability.
• Restructure pixi map panel.
• Extract ScreenMenu component out of title screen.
• Add PopupMenu component.
• Implement pause menu, with 'Resume' and 'Quit' options.

Closes #36