[3.0.4] - Fix bugs

• Fix the bug which photo can't be display in pub.dev

[3.0.5] - Add Scaffold and AppBar Widget

• Add Scaffold and AppBar Widget.
• Fix bugs.

[3.0.6] - bug fixed

• Fix the bug, https://github.com/dengyin2000/dynamic_widget/issues/64

[4.0.0-nullsafety.1] - null safety migration

• null safety migration

[4.0.0] - null safety migration

• null safety version released.

[4.0.1] - add ElevatedButtonParser

• add ElevatedButtonParser.

[4.0.2] - add DividerWidget and RotatedBox widget parser

• add DividerWidget and RotatedBox widget parser.