feat: save highscores

src/main/java/eu/midnightdust/yaytris/game/Space.java

@@ -65,6 +65,10 @@ public class Space {
         return gameMap;
     }
 
+    public int getScore() {
+        return score;
+    }
+
     public void onLinesChanged(Tetromino tetromino, int... lines) {
         int combo = 0;
         Set<Integer> completedLines = new TreeSet<>();