Work item - mobile ancestors widget

...s/components/work_item_ancestors/disclosure_hierarchy.vue

...ponents/work_item_ancestors/disclosure_hierarchy_item.vue

...ms/components/work_item_ancestors/work_item_ancestors.vue

...ts/javascripts/work_items/components/work_item_detail.vue

app/assets/stylesheets/page_bundles/work_items.scss

...mponents/work_item_ancestors/disclosure_hierarchy_spec.js

spec/frontend/work_items/components/work_item_detail_spec.js