Implement game main menu

[Greenheart]

Some ideas related to the game main menu. Should likely be broken down into subtasks and solved separately:

• show image, description, title to present game scenarios
• allow players to select game scenario to play
• allow players to save + load scenarios
• Add description of game, the community developing the game.
• Add CTA to help players who want to get involved and contribute to the game with content, code & art. (Basically this means providing Discord invite link pointing directly to the #swipeforfuture channel, where people are encouraged to say hi and we'll help them get started)

[Greenheart]

Idea for how to select the scenario you want in the main menu: swipe through a carousel where special cards are shown, containing details about the scenario. Start scenario by pressing a button below the card.

1. swipe carousel to select scenario and read more about it
2. press button to start