Add Pangeo button off of main page

Author: jmunroe

portal/index.md

@@ -26,6 +26,11 @@ Donate to support Project Pythia!
 
 {button}`Learn More →<./about.md>`
 
+{button}`About Pangeo →<https://pangeo.io>`
+
+{button}`[About Pangeo](https://pangeo.io)`
+
+
 [Project Pythia](./about.md) is the education working group for [Pangeo](https://pangeo.io)
 and is an educational resource for the entire geoscience community.
 Together these initiatives are helping geoscientists make sense of huge volumes of