Added support for running a function before the draw() function of a widget, for example when a widget needs to fetch additional user informations that aren't provided by the metadatas
/**
* @param {Page[]} pages
* @param {number} [id] Specifies the id, if applicable.
* @param {String} [title = This is untitled.] Specifies the title.
*/
function Document(pages, id, title){
}