increase the maximum number of columns when creating a new filter view for the list view

In times of big monitors, we can easily have more than 12 columns per list view. I just increased the value in layouts/vlayout/modules/CustomView/resources/CustomView.js to 15. But soon this can be even more. Let me know if I should just create a merge request for the changed value or if you want this to be added through the config, somewhat more sustainable and adjustable for each installation.