Add support for storage size to groups_list_item.vue

Proposal

Add support for storage size badge to app/assets/javascripts/vue_shared/components/groups_list/groupss_list_item.vue

Implementation guide

• In app/assets/javascripts/vue_shared/components/groups_list/groups_list_item.vue#L179 check for group.rootStorageStatistics.storageSize
• If group.rootStorageStatistics.storageSize is exists, render GlBadge with the numberToHumanSize util for formatting