Add support for fake input in asciicast recordings

* Fixes a bug with `SelectionPrompt` and page size.
* Allow `IAnsiConsoleInput` to return `null`.

resources/scripts/Generator/Commands/AsciiCast/Samples/TreeSample.cs

@@ -0,0 +1,39 @@
+using Spectre.Console;
+
+namespace Generator.Commands.Samples
+{
+    internal class TreeSample : BaseSample
+    {
+        public override void Run(IAnsiConsole console)
+        {
+            // Create the tree
+            var tree = new Tree("Root")
+                .Style(Style.Parse("red"))
+                .Guide(TreeGuide.Line);
+
+            // Add some nodes
+            var foo = tree.AddNode("[yellow]Nest objects like tables[/]");
+            var table = foo.AddNode(new Table()
+                .RoundedBorder()
+                .AddColumn("First")
+                .AddColumn("Second")
+                .AddRow("1", "2")
+                .AddRow("3", "4")
+                .AddRow("5", "6"));
+
+            table.AddNode("[blue]with[/]");
+            table.AddNode("[blue]multiple[/]");
+            table.AddNode("[blue]children too[/]");
+
+            var bar = tree.AddNode("Any IRenderable can be nested, such as [yellow]calendars[/]");
+            bar.AddNode(new Calendar(2020, 12)
+                .Border(TableBorder.Rounded)
+                .BorderStyle(new Style(Color.Green3_1))
+                .AddCalendarEvent(2020, 12, 12)
+                .HideHeader());
+
+            console.Write(tree);
+
+        }
+    }
+}