fix: 🐛 Added mounted check before setState in _reverseAnimateTooltip

- Added mounted check before `setState` in `_reverseAnimateTooltip` as this maybe called when widget is unmounted as this may be called when user taps very quickly and widget gets unmounted which throws error

lib/src/showcase.dart

@@ -510,6 +510,7 @@ class _ShowcaseState extends State<Showcase> {
   /// Reverse animates the provided tooltip or
   /// the custom container widget.
   Future<void> _reverseAnimateTooltip() async {
+    if (!mounted) return;
     setState(() => _isTooltipDismissed = true);
     await Future<dynamic>.delayed(widget.scaleAnimationDuration);
     _isTooltipDismissed = false;