added alias for textarea

Author: yanhick

cocktail/Dom.hx

@@ -22,6 +22,7 @@ typedef Style = cocktail.core.css.CSSStyleDeclaration;
 typedef Window = cocktail.core.window.Window;
 typedef Document = cocktail.core.html.HTMLDocument;
 typedef FormElement = cocktail.core.html.HTMLInputElement;
+typedef TextArea = cocktail.core.html.HTMLTextAreaElement;
 
 typedef Event = cocktail.core.event.Event;
 typedef MouseEvent = cocktail.core.event.MouseEvent;