Update emoji support

* Add constants for emojis
* Move emoji shortcode rendering to Markup
* Add documentation
* Add example
* Add tests

docs/Program.cs

@@ -19,6 +19,7 @@ namespace Docs
                 .ConfigureDeployment(deployBranch: "docs")
                 .AddShortcode("Children", typeof(ChildrenShortcode))
                 .AddShortcode("ColorTable", typeof(ColorTableShortcode))
+                .AddShortcode("EmojiTable", typeof(EmojiTableShortcode))
                 .AddPipelines()
                 .RunAsync();