Add AsciiCast demos for docs

docs/src/Shortcodes/AsciicastShortcode.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using Statiq.Common;
+using System.Linq;
+
+namespace Docs.Shortcodes
+{
+    public class AsciiCastShortcode : SyncShortcode
+    {
+        public override ShortcodeResult Execute(KeyValuePair<string, string>[] args, string content, IDocument document, IExecutionContext context)
+        {
+            // in the future I'd like to expand this to have two tabs, one with the full color unicode version
+            // and a second with the default plain.
+            var cast = args.First(i => i.Key == "cast").Value;
+            var profile = args.FirstOrDefault(i => i.Key == "profile").Value ?? "rich";
+
+            return $"<asciinema-player src=\"/assets/casts/{cast}-{profile}.cast\" autoplay></asciinema-player>";
+        }
+    }
+}