Add pyvideo link

[Daniel-at-github]

Suggestion: Add pyvideo link https://pyvideo.org/events/pycon-sk-2019.html

Now, 2019.pycon.sk Raw video it's published in it.

And let the people in charge of 2019.pycon.sk media that, if they publish processed for 2019.pycon.sk (when all are available), they can replace what is published now just adding a comment in pyvideo/data#766 (or a PR with the changes).