Add DjangoCon Europe 2021 secondary track talks

[jonafato]

This is a copy of #1179 with a formatting fix. I'm creating a new branch with the original commit instead of adding a commit to the PR remote to avoid pushing to its main branch. Original pull request description:

During Djangocon 2021 there was a secondary track of talks. These were billed as "Workshops", but most of these were structured like regular talks, and were recorded in any case (since the entire conference was remote). So I think they warrant inclusion into PyVideos.

See them on the schedule here: https://2021.djangocon.eu/cfp/schedule/index.html#2021-06-02