Earlier this week, I synced with @ted and we went over the whole header/mobile nav together, and we talked about some minor UI improvements we could make. This diff addresses those improvements. The improvements that were made were:
# Increase the horizontal padding in the `MobileNav` so it lined up better with the header
# When a user hovered over the tabs or icons in the `MobileNav` we should show a lighter white
Depends on D7898