External CSS Option for SVGDocument

Added External Cascading Style Sheet Option to SVGDocument.

Source/SvgDocument.cs

@@ -64,6 +64,11 @@ namespace Svg
         /// </summary>
         public int Ppi { get; set; }
         
+        /// <summary>
+        /// Gets or sets an external Cascading Style Sheet (CSS)
+        /// </summary>
+        public string ExternalCSSHref { get; set; }        
+
         #region ITypeDescriptorContext Members
 
         IContainer ITypeDescriptorContext.Container
@@ -471,6 +476,9 @@ namespace Svg
 
             xmlWriter.WriteDocType("svg", "-//W3C//DTD SVG 1.1//EN", "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd", null);
             
+            if (!String.IsNullOrEmpty(this.ExternalCSSHref))
+                xmlWriter.WriteProcessingInstruction("xml-stylesheet", String.Format("type=\"text/css\" href=\"{0}\"", this.ExternalCSSHref));
+
             this.WriteElement(xmlWriter);
 
             xmlWriter.Flush();