Update README.md & CHANGELOG.md

+# 5.5.3
+- Bug Fix: Some widgets disapear because of parent rebuild.
+- Bug Fix: issue #362. Null check operator used on a null value when using ScreenUtil.init().
+- Re-add context to builder parameters **(users request)**.
+- Add some standard rebuild factors.
+
 # 5.5.2
 - Add rebuildFactor property
 - Bug Fix: False sizes when resizing

@@ -57,7 +57,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 
 Please set the size of the design draft before use, the width and height of the design draft.
 
-#### The first way (Recommended)
+#### The first way (You must use it once in your app)
 
 ```dart
 void main() => runApp(MyApp());