chore(drawer): added readme file

Author: svdimitr

drawer/template/template/readme.md

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+# Drawer as Side Navigation
+
+This sample project shows one way to use the [Telerik Drawer](https://demos.telerik.com/blazor-ui/drawer/overview) as a side navigation in your project.
+
+Key points of interest:
+
+* The Drawers [Template](https://docs.telerik.com/blazor-ui/components/drawer/templates#template) is used in order to control the rendering of the entire component. 
+
+* All the logic, styles and code related to the drawer are in the `~/Shared/MainLayout.razor` file. You should separate them according to your project structure and best practices.
+
+* Code comments in the file provide details.
+
+* CSS rules define the size of the various containers and scrolling:
+    * The drawer will take up the entire viewport.
+    * Scrolling happens in the content area of the drawer only.
+    * The sticky header stays above the content.
+    
+* The current page is denoted by the selected item in the drawer:
+    * On initial load it is taken from the Data collection with the help of the `NavigationManager`.
+    * On SPA navigation, the navigation happens in the `@Body` so the click selects the item and it does not dispose
+    
+* In this sample, the list of links is hardcoded for brevity. You can populate it later based on user roles and privileges or any other applicable business logic.