docs(common): add breaking changes info for 1.3.0

Author: marin-bratanov

upgrade/breaking-changes/1-3-0.md

@@ -0,0 +1,13 @@
+---
+title: 1.3.0
+description: Handle the changes in the 1.3.0 release of the Telerik UI for Blazor components.
+page_title: Breaking Changes in 1.3.0
+slug: changes-in-1-3-0
+position: 1
+---
+
+# Breaking Changes in 1.3.0
+
+In the `1.3.0` release, the new `<TelerikRootComponent>` must be added to the root of the application.
+
+It is required for rendering detached popup elements so they can have correct (expected) positions and overflow behavior. You can read more about it in the [What You Need: Project Configuration]({%slug getting-started/what-you-need%}#project-configuration) article.