A version of JupyterLab that is reasonably feature-complete and stable enough to be usable for day-to-day work. Most of the major features of the classic notebook will be implemented and usable, but some of the minor ones will not yet be implemented. There will also be many new features not in the classic notebook.

See #3299 for the release schedule/plans.

After we reach this milestone, the project enters beta status. We'll continue to release 0.x.x versions until we've satisfied the Milestone 1.0 criteria.