Sets the size of a dialog window.
If width and height are set to `0, 0`, the size is automatically determined.
dlg_set_size(handle, width, height)
Set a dialog's size to 500×400 pixels
dlg_set_size("dialog_123", 500, 400);
Automatically determine the dialog's size
dlg_set_size("dialog_123", 0, 0);