Created first action and basic timer reducer

Signed-off-by: Andreas Fahrecker <AndreasFahrecker@gmail.com>

lib/actions/timer_actions.dart

@@ -0,0 +1,9 @@
+import 'package:time_progress_calculator/models/timer.dart';
+
+abstract class Action {}
+
+class UpdateTimerAction extends Action {
+  final Timer updatedTimer;
+
+  UpdateTimerAction(this.updatedTimer);
+}