customize docfx logo

Author: WeihanLi

docfx.json

@@ -25,7 +25,8 @@
     ],
     "globalMetadata": {
       "_appName": "dotnet-talks",
-      "_appTitle": "dotnet-talks",
+      "_appTitle": ".NET Talks",
+      "_appLogoPath": "images/dotnet-logo.jpg",
       "_enableSearch": true,
       "pdf": false
     }