Updated docfx version, and added new theme (#145)

Author: GlebChili

.config/dotnet-tools.json

@@ -15,7 +15,7 @@
       ]
     },
     "docfx": {
-      "version": "2.61.0",
+      "version": "2.63.1",
       "commands": [
         "docfx"
       ]

docfx_project/docfx.json

@@ -71,10 +71,7 @@
       "_appFaviconPath": "images/favicon.ico"
     },
     "fileMetadataFiles": [],
-    "template": [
-      "default",
-      "templates/material"
-    ],
+    "template": ["default", "modern"],
     "postProcessors": [],
     "markdownEngineName": "markdig",
     "noLangKeyword": false,