update cookbook_gallery yaml with Radar cookbook (#255)

* update cookbook_gallery yaml with Radar cookbook

* add tags, rm py-art from description

Author: jukent

portal/_static/thumbnails/arm_logo.png

@@ -1,10 +1,10 @@
 - title: Radar Cookbook
   url: https://projectpythiatutorials.github.io/radar-cookbook/landing-page.html
   description: |
-    This Project Pythia Cookbook covers the basics of working with weather radar data in Python using Py-ART.
+    This Project Pythia Cookbook covers the basics of working with weather radar data in Python.
   authors:
   - name: Max Grover
-  thumbnail:
+  thumbnail: /_static/thumbnails/arm_logo.png
   tags:
     domains:
     - radar