update es.js
according to commit a new preview field was added, the spanish translation probably was taken from an automatic translator which sounds weird, I've updated such field.
@@ -3,7 +3,7 @@ define({
"postbox-author": "Nombre (opcional)",
"postbox-email": "E-mail (opcional)",
"postbox-website": "Sitio web (opcional)",
- "postbox-preview": "Avance",
+ "postbox-preview": "Vista preliminar",
"postbox-edit": "Editar",
"postbox-submit": "Enviar",
"num-comments": "Un Comentario\n{{ n }} Comentarios",
