Add Heading

Ooui/Heading.cs

@@ -0,0 +1,24 @@
+using System;
+
+namespace Ooui
+{
+    public class Heading : Element
+    {
+        public Heading (int level = 1)
+            : base ("h" + level)
+        {
+        }
+
+        public Heading (int level, string text)
+            : this (level)
+        {
+            Text = text;
+        }
+
+        public Heading (string text)
+            : this ()
+        {
+            Text = text;
+        }
+    }
+}