docs(packages/walkthrough/steps/34/README.md‎): Add xmlns:core to XML example

This pull request makes a small update to the XML view file by adding the sap.ui.core namespace as core. This change ensures that core UI5 controls and features can be referenced in the view.

Added the xmlns:core="sap.ui.core" namespace declaration to the XML view to enable usage of core UI5 controls.

Author: anitamalina

packages/walkthrough/steps/34/README.md

@@ -104,6 +104,7 @@ Instead of the `ObjectListItem` that we had before, we will now split the inform
 <mvc:View
 	controllerName="ui5.walkthrough.controller.InvoiceList"
 	xmlns="sap.m"
+	xmlns:core="sap.ui.core"
 	xmlns:mvc="sap.ui.core.mvc">
 	<Table
 		id="invoiceList"