Theia 0.9.0 later today

Heads-up: I plan to go ahead with the 0.9.0 release later today, in ~6 hours. So there is still time to merge low-risk PRs.

[original thread by Marc Dumais]

I am starting the release - please hold-off merging in main repo until I am done

Ok, all done. Thanks to all who contributed to this release.