feat: make an instance group from the library's free space

scripts/check.sh

@@ -178,6 +178,8 @@ check "right-clicking one hides it" \
 	contains "$WORKTREE/apps/app-frontend/src/App.vue" 'openSidebarMenu'
 check "an instance can be deleted from the sidebar" \
 	contains "$WORKTREE/apps/app-frontend/src/components/ui/QuickInstanceSwitcher.vue" 'askToDelete'
+check "the library's free space offers a new group" \
+	contains "$WORKTREE/apps/app-frontend/src/pages/Index.vue" 'openNewGroupModal()'
 check "the news section can be collapsed" \
 	contains "$WORKTREE/apps/app-frontend/src/App.vue" 'setNewsCollapsed'
 check "the right sidebar has a fold button" \