add code comments

viz/ts/svg/svg/Canvas/Canvas.ts

@@ -2,8 +2,21 @@
 
 namespace Canvas {
 
+    /**
+     * CSS style object model
+    */
     export interface ICSSStyle {
+
+        /**
+         * Apply CSS style to a given svg node element
+         * 
+         * @param node a given svg document node object
+        */
         Styling(node: SVGElement): SVGElement;
+        /**
+         * Generate css style string value from this 
+         * css style object model.
+        */
         CSSStyle(): string;
     }