Page Grid
Demo
![flutter_flex](https://user-images.githubusercontent.com/62440911/160254118-f5bfc0f8-003b-432c-84a4-795eb27b5c2f.gif)
How to use
PageGrid(
head: Container(color: Colors.yellow),
body: Container(color: Colors.red),
footer: Container(color: Colors.pink),
)
PageGrid(
mirror: true,
head: Container(color: Colors.yellow),
body: Container(color: Colors.red),
footer: Container(color: Colors.pink),
)
PageGrid(
mirror: true,
mobileFlex: const BodyFlex(footer: 0),
desktopFlex: const BodyFlex(),
head: Container(color: Colors.yellow),
body: Container(color: Colors.red),
footer: Container(color: Colors.pink),
)