Add extension method to get the cell width of a character

src/Spectre.Console/Extensions/CharExtensions.cs

@@ -0,0 +1,18 @@
+namespace Spectre.Console
+{
+    /// <summary>
+    /// Contains extension methods for <see cref="char"/>.
+    /// </summary>
+    public static class CharExtensions
+    {
+        /// <summary>
+        /// Gets the cell width of a character.
+        /// </summary>
+        /// <param name="character">The character to get the cell width of.</param>
+        /// <returns>The cell width of the character.</returns>
+        public static int GetCellWidth(this char character)
+        {
+            return Cell.GetCellLength(character);
+        }
+    }
+}