Add title screen

[BenLeadbetter]

Add a screen which is the first landing page when the game is started. A new game can be started from here. This page will also be important as further features come later down the line, like settings, loading a previous game, etc.

Acceptance Criteria

• The page should be implemented using the preexisting ratatui widgets.
• The screen should include a "start" button
• The screen should include an "exit" button