User-contributed code: Mapping Penguin Population Study Sites

Alison asked if I'd submit some [code from a Tweet](https://twitter.com/apreshill/status/1287932388379488257) as a contribution:.

- Title: Mapping Penguin Population Study Sites
- Author: Alex Cookson
- Description: This code shows how to create a map of Antarctica with a "polar orthographic" projection (looking at Antarctica from the bottom of the Earth). Shown on the map are over 600 sites from the [MAPPPD](http://www.penguinmap.com/mapppd) (Mapping Application for Penguin Populations and Projected Dynamics) project, as well as an annotation showing the Palmer Peninsula -- birthplace of the Palmer Penguins in the dataset!

The code is [here](https://github.com/tacookson/tidy-tuesday/blob/master/2020/2020-07-28%20(Palmer%20Penguins)/penguin-site-map.Rmd). This is just a simple example, so it's a short RMarkdown file with comments in the code. If you prefer something different, I'm more than happy to change it to suit what you'd like!