chore(drawer): improve readme and code comments on Template sample

Author: marin-bratanov

drawer/template/readme.md

@@ -1,6 +1,6 @@
-# Drawer as Side Navigation
+# Custom Template 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.
+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 - this sample uses the [Template](https://docs.telerik.com/blazor-ui/components/drawer/templates#template) of the component to implement its out-of-the-box functionality with custom application code (such as item selection, navigation) and to add the expand/collapse button inside the side panel, while still keeping the `@Body` in the `<Content>` so navigation does not affect the drawer.
 
 Key points of interest:
 
@@ -17,6 +17,6 @@ Key points of interest:
 
 * 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
+    * On SPA navigation, the navigation happens in the `@Body` so the click selects the item and it does not dispose it.
 
 * 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.

drawer/template/template/Shared/MainLayout.razor

@@ -138,6 +138,7 @@
 
     protected override void OnInitialized()
     {
+        // pre-select the initial page the user requests
         string currPage = _navMan.Uri;
         DrawerItem ActivePage = NavigablePages.Where(p => p.Url.ToLowerInvariant() == GetCurrentPage().ToLowerInvariant()).FirstOrDefault();
         if (ActivePage != null)
@@ -148,19 +149,22 @@
         base.OnInitialized();
     }
 
+    // sample custom navigation
     public void NavigateToPage(DrawerItem item)
     {
         SelectedItem = item;
         _navMan.NavigateTo(SelectedItem.Url);
     }
 
+    // helper method to get the current page
     public string GetCurrentPage()
     {
         string uriWithoutQueryString = _navMan.Uri.Split("?")[0];
         string currPage = uriWithoutQueryString.Substring(Math.Min(_navMan.Uri.Length, _navMan.BaseUri.Length));
         return string.IsNullOrWhiteSpace(currPage) ? "/" : currPage;
     }
 
+    // helper method to highlight the currently selected item
     public string GetSelectedItemClass(DrawerItem item)
     {
         if (SelectedItem == null)