Major version bump node (18->20) and jupyterhub-singleuser (3->5)#1359

yuvipanda merged 2 commits intojupyterhub:mainjupyterhub/repo2docker:mainfrom

consideRatio:pr/bump-node-jupyterhubconsideRatio/repo2docker:pr/bump-node-jupyterhubCopy head branch name to clipboard