docs: add json-based example for the extending expressions article (#1819)

Author: petar-i-todorov

designing-reports/connecting-to-data/expressions/extending-expressions/overview.md

@@ -13,7 +13,7 @@ previous_url: /expressions-extending-expressions, /designing-reports/connecting-
 
 Expressions can easily be extended by providing user functions written in any .NET language. This is very useful in addition to the built-in functions, providing more complex domain-specific calculations or uniform calculations because it speeds up the processing and boosts the performance. Furthermore, you can add custom aggregate functions to apply domain-specific logic while accumulating values.
 
-In order to expose your custom functions, so they can be utilized by the Reporting engine, you have to add a reference to the assembly they are defined in. The reference is added under the AssemblyReferences configuration section in the application's configuration file.
+In order to expose your custom functions, so they can be utilized by the Reporting engine, you have to add a reference to the assembly they are defined in. This can be done through the [assemblyReferences element]({%slug telerikreporting/using-reports-in-applications/export-and-configure/configure-the-report-engine/assemblyreferences-elementAssemblyReferences%}) in the application's configuration file.
 
 ````XML
 <configuration>
@@ -26,12 +26,22 @@ In order to expose your custom functions, so they can be utilized by the Reporti
 	</configSections>
 	…
 	<Telerik.Reporting>
-		<AssemblyReferences>
+		<assemblyReferences>
 			<add name="MyCustomAssembly" version="1.0.0.0" />
-		</AssemblyReferences>
+		</assemblyReferences>
 	</Telerik.Reporting>
 </configuration>
 ````
+````JSON
+"telerikReporting": {
+    "assemblyReferences": [
+        {
+            "name": "MyCustomAssembly",
+            "version": "1.0.0.0"
+        }
+    ]
+}
+````
 
 ## See Also