- Updates "Start a call", documents the "Jitsi server URL" setting,
and links to it in a (?) from the relevant admin UI.
- Fixes misplaced include block for opening the compose box.
Fixes#26907.
These files are not Jinja2 templates, so there's no reason that they needed
to be inside `templates/zerver`. Moving them to the top level reflects their
importance and also makes it feel nicer to work on editing the help center content,
without it being unnecessary buried deep in the codebase.
David Rosa
Karl Stolley
N-Shar-ma
Lauryn Menard