practice RWD with MUI

Progress

• Define needed component & state in useContext (2hr)
• Finished Stepper and StepController (2hr)
• Finished Step1 to Step4 (2hr)
• enable cartInfo and setCartInfo access to Step1 ~ Step4 (4hr)
• Design view for desktop (4hr)

What did I learn?

• first time to try RWD for mobile and desktop in the same time.

Since Stepper, StepController, and banner would set up different position, I create different pages for mobile and desktop. Wondering if there's a wisely way.

Continued development

• since some of css change conditionally, I should define css in the component rather than in css file.
• MUI style setting should edit in themeProvider rather than in inline .