Add interactive prompts for selecting values

* Adds SelectionPrompt
* Adds MultiSelectionPrompt

Closes #210

docs/input/prompts/selection.md

@@ -0,0 +1,27 @@
+Title: Selection
+Order: 1
+---
+
+The `SelectionPrompt` can be used when you want the user to select
+a single item from a provided list.
+
+<img src="../assets/images/selection.gif" style="width: 100%;" />
+
+# Usage
+
+```csharp
+// Ask for the user's favorite fruit
+var fruit = AnsiConsole.Prompt(
+    new SelectionPrompt<string>()
+        .Title("What's your [green]favorite fruit[/]?")
+        .PageSize(10)
+        .AddChoice("Apple")
+        .AddChoices(new[] {
+            "Apricot", "Avocado", 
+            "Banana", "Blackcurrant", "Blueberry",
+            "Cherry", "Cloudberry", "Cocunut",
+        }));
+
+// Echo the fruit back to the terminal
+AnsiConsole.WriteLine($"I agree. {fruit} is tasty!");
+```