Gets the data passed to a custom app page.
Wix passes data to custom app pages that you can use when implementing a page's business logic.
Call the getAppPageData() method to retrieve the data and use it in your code.
The data retrieved by this method is different for each type of custom app page.
For more information, see App Page Data.
Learn more about building custom app pages.
Note: If you call getAppPageData() for a page that isn't
a custom app page, it returns null.