Add script to select videos from URL fragment; thanks ndegruchy

based on https://gist.github.com/ndegruchy/6ef8804cc0d8c21d9d6b8b7dd2d6be98
Set conf pages doctypes; put head in elements.fnl.
Add id attributes to video links.
Add watch buttons and <video> element for conf talks.
User group is now in PDT.
Bump to Fennel 1.4.2 submodule.
Colored survey graphs.
Bump fennel submodule to 1.4.1.
Update security page.
Style the pre elements on the security page.
Actually generate security.html from Fennel.
Tweak known_hosts some more.
Use my own mirror of fennel-highlight.

The original repo is now a 404: https://github.com/firoxer/fennel-highlight/
Update known_hosts for new SSH server key.
Conf talks have video links now!
Update wiki to use fennel shebang directly.

The hosting company moved us to a new machine that doesn't have its
own lua.
Make sure all the conf links are updated to 2023.
FennelConf 2024 is done!
Minor homepage wording changes.
Add schedule for 2023 conf.