New Ticker Mixin for AnimationController.

- Added SingleGetTickerProviderMixin to rx_interface.dart, usage like SingleTickerProviderMixin in a StatefulWidget, but only valid for DisposableInterfaces.

@@ -72,3 +72,25 @@ abstract class DisposableInterface {
   /// Might be useful as well to persist some data on disk.
   void onClose() async {}
 }
+
+/// Used like [SingleTickerProviderMixin] but only with Get Controllers.
+/// Simplifies AnimationController creation inside GetxController.
+///
+/// Example:
+///```
+///class SplashController extends GetxController with SingleGetTickerProviderMixin {
+///  AnimationController _ac;
+///
+///  @override
+///  void onInit() {
+///    final dur = const Duration(seconds: 2);
+///    _ac = AnimationController.unbounded(duration: dur, vsync: this);
+///    _ac.repeat();
+///    _ac.addListener(() => print("Animation Controller value: ${_ac.value}"));
+///  }
+///  ...
+/// ```
+mixin SingleGetTickerProviderMixin on DisposableInterface
+    implements TickerProvider {
+  Ticker createTicker(TickerCallback onTick) => Ticker(onTick);
+}