checkmark for each list element

[Ykernerm]

As a user I want to experience a sense of achievement after reaching each step in order to keep the motivation for finishing all the steps.
acceptance criteria:
Step 1: Add a checkmark for each list element and disable them
Step 2: Checkmark only appears near the page title in the list after the user finished reading the page.

• If the user clicks next, the previous item in the list gets a checkmark, which stays on throughout the whole journey.

Style Guide + Figma File: https://www.figma.com/file/UlFgJ7Z4EAxzIB0FqiQbfA/DevonVisualization?node-id=0%3A1