changed image format from svg to png

Author: adam-burns

hugo-gh/content/_index.md

@@ -4,5 +4,5 @@ title: "The Rise of the Network Commons"
 description: "A History of Community Infrastructure by Armin Medosch"
 # 1. To ensure Netlify triggers a build on our exampleSite instance, we need to change a file in the exampleSite directory.
 #cascade:
-featured_image: '/images/back-cover-gfx.svg'
+featured_image: '/images/back-cover-gfx.png'
 ---