Skeleton loader guidelines need to be updated to include 2 color elements
This is coming from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9197
Skeleton loaders need to represent the elements that will be loaded in. Currently, our guidelines support very simple atoms to be represented by a single color (which will then use a second color to pulse over it in the loading animation). However, sometimes we need to represent a molecule instead of just an atom. This requires 2 colors and animation to match.