[client] Add in-game UI

[lunacys]

• [ ] Login/registration screen
• [ ] Main menu
• [ ] Single player
  • [ ] Vs Bot
  • [ ] 40 lines best time
  • [ ] 2 minutes highest score
• [ ] Multiplayer
  • [ ] Lobby list, ability to join lobbies
  • [ ] Lobby screen
    • [ ] Current players
    • [ ] Match settings
• [ ] Game settings

[lunacys]

Related to #21