Make mobile settings navigation component

[ryanml]

Design:

This is an ever present stick navigation element for mobile rewards. At the root of brave://rewards this will display a toggle for Brave Rewards being enabled, and the rewards title

As you open a box detail view such as auto-contribute, the navigation element should update with the title for auto-contribute, as well as house the toggle for auto-contribute. A "Back" arrow (<-) can be clicked at this point to go back to the main rewards settings. If inside the detail view the box-specific settings page is visited, the back button will then drive back to the box detail view. There is for now a maximum of 3 levels in depth you can go in the settings page that this component should keep track of.

[ryanml]

This is actually part of #172