Add Callback.alert

Author: japgolly

core/src/main/scala/japgolly/scalajs/react/Callback.scala

@@ -83,6 +83,12 @@ object Callback {
   def assert(test: Boolean, message: String, optionalParams: js.Any*): Callback =
     Callback(console.assert(test, message, optionalParams: _*))
 
+  /**
+   * Convenience for calling `dom.alert`.
+   */
+  def alert(message: String): Callback =
+    Callback(org.scalajs.dom.alert(message))
+
   /**
    * Serves as a temporary placeholder for a callback until you supply a real implementation.
    *