feat: save highscores

src/main/java/eu/midnightdust/yaytris/Tetris.java

@@ -25,6 +25,7 @@ public class Tetris {
             UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
         } catch (Exception | Error e) { System.out.printf("%s: %s\n", "Error setting system look and feel", e); }
         Settings.load();
+        HighScores.load();
         timer = new Timer("Tetris falling pieces");
         space = new Space();
         ui = new TetrisUI();
@@ -51,6 +52,7 @@ public class Tetris {
 
     public static void stopGame() {
         SoundUtil.stopMusic("/music/theme.wav");
+        HighScores.addScore(space.getScore());
         if (gravityTask != null) gravityTask.cancel();
         timer.purge();
         if (ui.getMenuPanel() instanceof ScoreMenu) ((ScoreMenu) ui.getMenuPanel()).gameOver();