[Material] Currently cannot set the background on Material Steppers

Description

To achieve a similar look we reused the Material Buttons (since they had already painstakingly been worked on to look the same) to create a Material Stepper on iOS and Android. For this we used the Outline Style which doesn't by default render a background color

Steps to Reproduce

Expected Behavior

Each stepper should be purple

Actual Behavior

Each stepper is not purple

Possibly other improvements

Add TextColor property so the text color of the stepper itself can be changed