Allows asking the user to select a file. It is not GUI view like other JS GUI views, rather just a function that shows a prompt.
For an example, refer to the gui.js example script.
Displays a file picker and returns the selected file, or undefined if cancelled.
Parameters
basePath: the path to start atextension: the file extension(s) to show (like .sub, .iso|.img, *)Returns
A string path, or undefined.