Refactor main menu with scene2d

Refactor the MainMenuScreen and MainMenuController to use scene2d. Use the same approach as for LoginScreen.

added 🎨 area::UI/UX 📝 type::task 🖥 frontend 🚨 priority::critical 🛠 Working on labels

assigned to @sanderof

created branch 28-refactor-main-menu-with-scene2d to address this issue

mentioned in merge request !29 (merged)

changed milestone to %Sprint 2: Multiplayer implementation

mentioned in commit 0e176e7e

closed with merge request !29 (merged)

removed 🛠 Working on label