Implement mobile navigation header and footer

Implement the new native designs for the nav bar

This should be behind the new navigation feature flag setup for the front end

This card is to set up the new look and feel for the new mobile designs

https://projects.invisionapp.com/d/main#/console/18532170/400085462/preview

Top nav

• New title on the top left
• Messenger icon with notifications
• Search button

Bottom nav

• Home button
• Channel button
• + add new activity button
• Notification icon
• hamburger menu

Overall design

• Light mode
• Dark mode