Add async spinner extension methods and related documentation

docs/input/live/async.md

@@ -0,0 +1,73 @@
+Title: Async Extensions
+Order: 11
+Description: "Async Extensions provides extension methods for running tasks with an inline animations."
+Highlights:
+    - Extension methods for running tasks with spinner animations
+    - Support for both void and generic Task types
+    - Customizable spinner styles and console output
+Reference:
+    - T:Spectre.Console.Extensions.SpinnerExtensions
+Xref: spinner-extensions
+---
+
+The Async Spinner Extension provides convenient extension methods for running tasks with an inline spinner animations in the console.
+
+<?# AsciiCast cast="await-spinner" /?>
+
+<?# Alert ?>
+  The spinner animation is not thread safe, and using it together with other interactive 
+  components such as prompts, progress displays or other status displays is not supported.
+<?#/ Alert ?>
+
+## Usage
+
+The extension methods allow you to easily add spinner animations to any Task execution:
+
+```csharp
+// Basic usage with void Task
+await someTask.Spinner();
+
+// With generic Task<T>
+var result = await someTaskWithResult.Spinner(
+    Spinner.Known.Star,
+    new Style(foreground: Color.Green));
+
+// With custom console
+await someTask.Spinner(
+    Spinner.Known.Dots,
+    style: Style.Plain,
+    ansiConsole: customConsole);
+```
+
+## Features
+
+The spinner extensions provide:
+
+- Support for both void Tasks and Tasks with return values
+- Customizable spinner animations using any Spectre.Console Spinner
+- Optional styling for the spinner animation
+- Ability to specify a custom IAnsiConsole instance
+
+## Examples
+
+Here's a more complete example showing different ways to use the spinner extensions:
+
+```csharp
+// Basic spinner with default settings
+await Task.Delay(1000)
+    .Spinner(Spinner.Known.Dots);
+
+// Customized spinner with style
+var result = await CalculateSomething()
+    .Spinner(
+        Spinner.Known.Star,
+        new Style(foreground: Color.Green));
+
+// Using with a custom console
+await ProcessData()
+    .Spinner(
+        new Spinner(new[] { "⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏" }, 80),
+        new Style(foreground: Color.Blue),
+        customConsole);
+```
+