Better child widget managements within `App` widget.
Better child widget managements within `App` widget.

Closes #29
Closes #25

agrc/fiber-verification,agrc/fiber-verification,agrc/AGRCJavaScriptProjectBoilerPlate,agrc/AGRCJavaScriptProjectBoilerPlate,agrc/AGRCJavaScriptProjectBoilerPlate,agrc/fiber-verification