User should see exit signs in the Instruction Banner

[Guardiola31337]

When a user is traveling down a motorway, any "Exit" instructions should be styled to be very distinguishable.

Refs mapbox/mapbox-navigation-ios#1262

[andrewychen]

@okoriep noticed differences in use of highway shields between 2 different Android phone models.

[Guardiola31337]

noticed differences in use of highway shields between 2 different Android phone models.

This ticket tracks adding exit signs support. Shouldn't we cut a new ticket for ☝️? This issue seems unrelated to OP @andrewychen

cc @okoriep

[danesfeder]

Inconsistent shield issue #992 is already ticketed.