refactor: make all GameOptions optional with sensible defaults

- cols defaults to 30 (was required)
- rows defaults to 20 (was required)
- timeLimit and startingLevel remain optional
- Can now call useGame() with no arguments
- Example: useGame(), useGame({}), useGame({ startingLevel: 5 })

src/types.ts

@@ -29,8 +29,8 @@ export type SnakeBody = Position[];
 export type KeyLogEntry = { key: string; timestamp: number };
 
 export type GameOptions = {
-  cols: number;
-  rows: number;
+  cols?: number;
+  rows?: number;
   timeLimit?: number;
   startingLevel?: number;
 };