- Corrects documentation to reflect that typing notifications also
work when narrowing to all direct messages in the web/desktop app,
and disappear under certain conditions.
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.