Add Champions lessons

[jules32]

Following the addition of the 3 previous Champions Cohorts to the Workshops page (#353), let's add the Champions lessons in one place to the Cookbook so we can find them easily and see the progression of lessons.

Currently lessons live in the Champions Series: https://openscapes.github.io/series/, and there are summaries to draw from in each of the blog posts listed https://nasa-openscapes.github.io/champions.html#learn-more.

[ateucher]

This is a great idea!