Fix: ⚡ Improved showCaseWidgetState variable in Showcase class

- Improved `showCaseWidgetState` variable in `Showcase` class by removing getter as getter will compute that variable every time thus reducing performance
- Updated `CHANGELOG.md`

CHANGELOG.md

@@ -1,4 +1,11 @@
 ## [2.0.4] (Un-Released)
+- Improvement [#413](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/pull/413) - Improved `Showcase` class
+- Fixed [#369](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/pull/369) - Fixed ToolTip Slide Transition
+- Fixed [#388](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/issues/388) - Can't scroll horizontal list with showcase
+- Fixed [#366](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/issues/366) - Null check operator used on a null value
+- Fixed [#389](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/issues/389) - Ignore extra `_nextIfAny` function operations
+- Fixed [#409](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/pull/409) - Fixed target hit area.
+- Improvement [#370](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/pull/370) - Improved `GetPosition` class.
 - Feature [#387](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/issues/387) - Provided barrier click disable functionality for a particular showcase.
 - Fixed [#383](https://github.com/SimformSolutionsPvtLtd/flutter_showcaseview/issues/383) - Targeted widget focusing issue when we applying size constraint on root widget(MaterialApp).
 - Improved internal `findRenderObject` calls.

lib/src/showcase.dart

@@ -371,7 +371,7 @@ class _ShowcaseState extends State<Showcase> {
   Size? rootWidgetSize;
   RenderBox? rootRenderObject;
 
-  ShowCaseWidgetState get showCaseWidgetState => ShowCaseWidget.of(context);
+  late final showCaseWidgetState = ShowCaseWidget.of(context);
 
   @override
   void initState() {