Put CSS that has been brought home in /subfont, make sure to add an e…

…xtension, and add content hash to the file name

lib/subfont.js

@@ -117,7 +117,7 @@ module.exports = async ({
         new Error(`Pulling down modified stylesheet ${asset.url}`)
       );
       asset.url =
-        assetGraph.root + (asset.fileName || `index${asset.defaultExtension}`);
+        `${assetGraph.root}subfont/${asset.baseName || 'index'}-${asset.md5Hex.slice(0, 10)}${asset.extension || asset.defaultExtension}`;
     }
   }