Include bg switcher for illustrations
Problem
Illustrations don’t always appear on a white background and it is difficult in the previewer to see what they look like on a different background. This will be critical for dark UI or illustrations placed on a background other than white.
Solution
Use a similar configuration panel as the icons do to change the background color behind each illustration. The default background color will be white, like the icon backgrounds. Note that this change also updates the colors used to match hex values from GitLab UI. Illustrations may not always appear on these background colors, it is only designed as a test and uses the same config as the icons.
Edited by Jeremy Elder