feat: Add toc.json transform logics using toc.extension.js (#9953)

feat: Add toc.json transform logics

Author: filzrev

templates/default/toc.extension.js

@@ -2,14 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 /**
- * This method will be called at the start of exports.transform in toc.html.js
+ * This method will be called at the start of exports.transform in toc.html.js and toc.json.js
  */
 exports.preTransform = function (model) {
   return model;
 }
 
 /**
- * This method will be called at the end of exports.transform in toc.html.js
+ * This method will be called at the end of exports.transform in toc.html.js and toc.json.js
  */
 exports.postTransform = function (model) {
   return model;

templates/default/toc.json.js

@@ -1,11 +1,20 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
+var extension = require('./toc.extension.js')
 
 exports.transform = function (model) {
 
+    if (extension && extension.preTransform) {
+      model = extension.preTransform(model);
+    }
+
     if (model.memberLayout === 'SeparatePages') {
       model = transformMemberPage(model);
     }
+
+    if (extension && extension.postTransform) {
+      model = extension.postTransform(model);
+    }
 
     for (var key in model) {
       if (key[0] === '_') {