cleaning on unregister
after plugin is unregistered the listeners added to dom (here: https://git-r3lab.uni.lu/minerva/plugins/guide/blob/master/src/js/index.js#L428) are not removed
after plugin is unregistered the listeners added to dom (here: https://git-r3lab.uni.lu/minerva/plugins/guide/blob/master/src/js/index.js#L428) are not removed