Implementing Timer and its examples

doc/examples/timer/lib/main.dart

@@ -0,0 +1,45 @@
+import 'package:flutter/gestures.dart';
+import 'package:flutter/material.dart';
+import 'package:flame/flame.dart';
+import 'package:flame/game.dart';
+import 'package:flame/time.dart';
+import 'package:flame/text_config.dart';
+import 'package:flame/position.dart';
+
+void main() {
+  final game = MyGame();
+  runApp(game.widget);
+
+  Flame.util.addGestureRecognizer(TapGestureRecognizer()
+    ..onTapDown = (TapDownDetails evt) {
+      game.countdown.start();
+    });
+}
+
+class MyGame extends Game {
+  final TextConfig textConfig = TextConfig(color: const Color(0xFFFFFFFF));
+  Timer countdown;
+  Timer interval;
+
+  int elapsedSecs = 0;
+
+  MyGame() {
+    countdown = Timer(2);
+    interval = Timer(1, repeat: true, callback: () {
+      elapsedSecs += 1;
+    });
+    interval.start();
+  }
+
+  @override
+  void update(double dt) {
+    countdown.update(dt);
+    interval.update(dt);
+  }
+
+  @override
+  void render(Canvas canvas) {
+    textConfig.render(canvas, "Countdown: ${countdown.current.toString()}", Position(10, 100));
+    textConfig.render(canvas, "Elapsed time: $elapsedSecs", Position(10, 150));
+  }
+}