Compose a theme template visualizer

Finding all classes and styling all necessary components can be tedious. We can make this a little bit easier by adding a snapshot test that renders all stylable UIViews and UIControls in the same image that we can link to from our documentation. This would help w/ connecting the class name to a stylable component but also visualize the entire theme.

I'm thinking something like the navigation view, but for all components that can be visible at any given time, including the sub banner and hidden buttons.

func draw(views: [UIView & Stylable], using style: Style) { 
    // Draw all views using `style`
    FBSnapshotVerifyView(containerView)
}

/**
 A view that represents the root view of the MapboxNavigation drop-in UI.
 
 ## Components
 
 1. InstructionsBannerView
 2. InformationStackView
 3. BottomBannerView
 4. ResumeButton
 5. WayNameLabel
 6. FloatingStackView
 7. NavigationMapView
 
 +--------------------+
 |         1          |
 +--------------------+
 |         2          |
 +----------------+---+
 |                |   |
 |                | 6 |
 |                |   |
 |         7      +---+
 |                    |
 |                    |
 |                    |
 +------------+       |
 |  4  ||  5  |       |
 +------------+-------+
 |         3          |
 +--------------------+
*/

@mapbox/navigation-ios

Start by reading the existing navigation view and the snapshot-test usage represented by FBSnapshotVerifyView. Identify the stylable UIViews and UIControls, including the listed navigation components and hidden buttons, then verify that one rendered image covers the full themed layout and can be linked from the documentation.