Implement frontend when exiting review form

[songmichael11]

Description

Currently, nothing happens when someone tries exiting the review form while they have information inputted in. We want a popup to appear that stops them exiting

TODO

• Following the Figma, implement the popup design for mobile and non-mobile
  • The popup should appear when a user tries exiting the form and when they have any information inputted in
• Don't worry about implementing the "Save Draft" button atm, just focus on styling for now