docs(dialog): Include an example of configuring the default input text in a prompt dialog. (#1514)

Author: yanisslav

components/dialog/predefined.md

@@ -114,6 +114,7 @@ The prompt dialog returns a `string` that the user enters when they press `OK`,
 
 <TelerikButton OnClick="@ShowPrompt">Show Prompt</TelerikButton>
 <TelerikButton OnClick="@ShowPromptWithTitle">Show Prompt with Custom Title</TelerikButton>
+<TelerikButton OnClick="@ShowPromptWithTitleAndDefaultText">Show Prompt with Title and Default Input Text</TelerikButton>
 
 @code {
     [CascadingParameter]
@@ -139,6 +140,13 @@ The prompt dialog returns a `string` that the user enters when they press `OK`,
 
         Console.WriteLine($"The user answer: {userInput}");
     }
+
+    async Task ShowPromptWithTitleAndDefaultText()
+    {
+        string userInput = await Dialogs.PromptAsync("Enter answer:", "Input needed", "Default Text");
+
+        Console.WriteLine($"The user answer: {userInput}");
+    }
 }
 ````