Add missing NuGet package reference.

code/TemplateStudioForWinUICs/Templates/Proj/Default/.template.config/template.json

@@ -96,15 +96,26 @@
       "continueOnError": true
     },
     {
-      "description": "Add nuget package",
-      "manualInstructions": [ ],
-      "actionId": "0B814718-16A3-4F7F-89F1-69C0F9170EAD",
-      "args": {
-        "packageId": "Microsoft.WindowsAppSDK",
-        "version": "1.0.1",
-        "projectPath": "Param_ProjectName\\Param_ProjectName.csproj"
-      },
-      "continueOnError": true
+        "description": "Add nuget package",
+        "manualInstructions": [],
+        "actionId": "0B814718-16A3-4F7F-89F1-69C0F9170EAD",
+        "args": {
+            "packageId": "Microsoft.WindowsAppSDK",
+            "version": "1.0.1",
+            "projectPath": "Param_ProjectName\\Param_ProjectName.csproj"
+        },
+        "continueOnError": true
+    },
+    {
+        "description": "Add nuget package",
+        "manualInstructions": [],
+        "actionId": "0B814718-16A3-4F7F-89F1-69C0F9170EAD",
+        "args": {
+            "packageId": "Newtonsoft.Json",
+            "version": "13.0.1",
+            "projectPath": "Param_ProjectName.Core\\Param_ProjectName.Core.csproj"
+        },
+        "continueOnError": true
     },
     {
       "description": "Add reference to core project",