Documents new wildcard mention for topic participants updating
and making tweaks to all relevant pages.
Fixes#27657.
Co-authored-by: Alya Abbott <alya@zulip.com>
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.
Alya Abbott
David Rosa
Lauryn Menard