Add the CSSStyleRule.style property. (scala-js#405)

Author: shaneorama

src/main/scala/org/scalajs/dom/raw/Css.scala

@@ -308,6 +308,13 @@ class CSSStyleRule extends CSSRule {
    */
   var selectorText: String = js.native
   var readOnly: Boolean = js.native
+
+  /**
+   * Returns the CSSStyleDeclaration object for the rule.
+   *
+   * MDN
+   */
+  val style: CSSStyleDeclaration = js.native
 }
 
 /**