Create goal interface

Is your feature related to a problem? Please describe.

When the player starts a game, there are several goals for the player to reach. It should be easy to create new goals with different values.

Describe the solution you'd like.

The image below describes the proposed solution. The goal interface has the method isFulfilled(player: Player) which each goal needs to implement. All goals can be stored in a list and checked if it is fulfilled. When implemented, add the goal list to the game class