Add Element.matches which has all modern browser support

Author: er1c

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

@@ -817,6 +817,15 @@ abstract class Element
    */
   def insertAdjacentHTML(where: String, html: String): Unit = js.native
 
+  /**
+   * The `matches()` method of the `Element` interface returns `true` if the
+   * element would be selected by the specified selector string; otherwise, it
+   * returns `false`.
+   *
+   * MDN
+   */
+  def matches(selector: String): Boolean = js.native
+
   /**
    * getAttribute() returns the value of the named attribute on the specified element.
    * If the named attribute does not exist, the value returned will either be null or ""