[Challenge] Create a `ChallengePlugin`

A challenge consists of

```ts
interface ChallengeDefinition {
id: string;
startConditions: Condition[];
endConditions: Condition[];
challengeModifiers: Bonus[];
rewards: Output[];
rewardBonuses: Bonus[];
autocomplete?: bool;
}
```

Then you can start a challenge and the modifiers will apply while its running. On completion you get the rewards and the new bonuses are active.