Add World Map Examples in Spatial Data Section

[spontacular]

The Spatial Data Section currently has examples of only US Maps and adding World Map examples to it could be more informative.
Additionally, while working on our EDAV Final Project, we noticed that the 'choropleth' package is not the best option for creating World Maps and we had to instead use the 'rworldmap' package.
We would be happy to contribute to the page through the code we wrote for our EDAV Final Project (If needed)