docs: add breaking changes for version 12 (#3340)

* docs: add breaking changes for version 12

* docs: reword the new changes

* docs: add api links

Author: IvanDanchev

upgrade/breaking-changes/12-0-0.md

@@ -0,0 +1,25 @@
+---
+title: 12.0.0
+description: Handle the changes in the 12.0.0 release of the Telerik UI for Blazor components.
+page_title: Breaking Changes in 12.0.0
+slug: changes-in-12-0-0
+position: 950
+---
+
+# Breaking Changes in 12.0.0
+
+## Chat
+
+The `MessageTemplate` parameter is renamed to `MessageContentTemplate`. `MessageTemplate` is still a valid template, but is used to replace the whole message bubble element.
+
+## Filter
+
+The `TelerikFilter.ValueChanged` event is now deprecated. Use the [`OnUpdate` event](slug:filter-events#onupdate) instead.
+
+## Pager
+
+The `TelerikPager.Adaptive` parameter is now deprecated. Use the [`Responsive` parameter](https://www.telerik.com/blazor-ui/documentation/api/telerik.blazor.components.telerikpager#telerik_blazor_components_telerikpager_responsive) instead. Parameters in setting tags like `GridPagerSettings.Adaptive`, `TreeListPagerSettings.Adaptive`, etc., are renamed to `Responsive`. For example, `GridPagerSettings.Responsive`.
+
+## ToolBar
+
+The `TelerikToolBar.Adaptive` parameter is now deprecated. Use the [`OverflowMode` parameter](https://www.telerik.com/blazor-ui/documentation/api/telerik.blazor.components.teleriktoolbar#telerik_blazor_components_teleriktoolbar_overflowmode) instead.

upgrade/breaking-changes/list.md

@@ -9,6 +9,7 @@ position: 0
 # List of Telerik UI for Blazor Versions with Breaking Changes
 
 This article lists the releases of the Telerik UI for Blazor product that introduce breaking changes. You may want to go through it when [upgrading](slug:upgrade-tutorial) to see whether you are affected.
+* [12.0.0](slug:changes-in-12-0-0)
 * [10.0.0](slug:changes-in-10-0-0)
 * [9.0.0](slug:changes-in-9-0-0)
 * [8.0.0](slug:changes-in-8-0-0)