Improve responsive design for mobile devices

[IsaacCheng9]

Specification

• The view on mobile devices needs improving, as it currently requires the user to side-scroll which is unintuitive.
• Investigate ways of improving the responsive design.
• A basic improvement would be to centre the FairSplit logo, move the user switcher to the top, and move the group members panel to the bottom of the page.
  • Top to bottom: FairSplit logo -> user switcher -> group expenses -> group members
• If it's feasible, we could look to have smarter switching between the group expenses and group members view.
  • Keep the FairSplit logo and user switcher elements static, and have a slide-deck style switcher between the group expenses and group members.
    • When the user scrolls vertically, it should switch between the two slide decks so that each view is fully displayed.

Screenshots