Add status support

docs/input/appendix/spinners.md

@@ -0,0 +1,43 @@
+Title: Spinners
+Order: 4
+---
+
+For all available spinners, see https://jsfiddle.net/sindresorhus/2eLtsbey/embedded/result/
+
+# Usage
+
+Spinners can be used with [Progress](xref:progress) and [Status](xref:status).
+
+```csharp
+AnsiConsole.Status()
+    .Spinner(Spinner.Known.Star)
+    .Start("Thinking...", ctx => {
+        // Omitted
+    });
+```
+
+# Implementing a spinner
+
+To implement your own spinner, all you have to do is 
+inherit from the `Spinner` base class.
+
+In the example below, the spinner will alterate between
+the characters `A`, `B` and `C` every 100 ms.
+
+```csharp
+public sealed class MySpinner : Spinner
+{
+    // The interval for each frame
+    public override TimeSpan Interval => TimeSpan.FromMilliseconds(100);
+    
+    // Whether or not the spinner contains unicode characters
+    public override bool IsUnicode => false;
+
+    // The individual frames of the spinner
+    public override IReadOnlyList<string> Frames => 
+        new List<string>
+        {
+            "A", "B", "C",
+        };
+}
+```