reverse engineering library setup from slider

https://work.montagestudio.com/app/5a2ed9b28a30fe67da6739522fc1837e6108e21a/extensions/digit.filament-extension/library-items/digit/slider.library-item/slider.html

for https://github.com/ProjetDeRechercheSurLecriture/DyslexDisorthGame/issues/158