Add support for table footers

src/Spectre.Console/Extensions/TableColumnExtensions.cs

@@ -0,0 +1,55 @@
+using System;
+using Spectre.Console.Rendering;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// Contains extension methods for <see cref="TableColumn"/>.
+    /// </summary>
+    public static class TableColumnExtensions
+    {
+        /// <summary>
+        /// Sets the table column footer.
+        /// </summary>
+        /// <param name="column">The table column.</param>
+        /// <param name="footer">The table column markup text.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static TableColumn Footer(this TableColumn column, string footer)
+        {
+            if (column is null)
+            {
+                throw new ArgumentNullException(nameof(column));
+            }
+
+            if (footer is null)
+            {
+                throw new ArgumentNullException(nameof(footer));
+            }
+
+            column.Footer = new Markup(footer);
+            return column;
+        }
+
+        /// <summary>
+        /// Sets the table column footer.
+        /// </summary>
+        /// <param name="column">The table column.</param>
+        /// <param name="footer">The table column footer.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static TableColumn Footer(this TableColumn column, IRenderable footer)
+        {
+            if (column is null)
+            {
+                throw new ArgumentNullException(nameof(column));
+            }
+
+            if (footer is null)
+            {
+                throw new ArgumentNullException(nameof(footer));
+            }
+
+            column.Footer = footer;
+            return column;
+        }
+    }
+}