- Adds a link to the "Recent conversations" article whenever we use the
term "conversation" as a technical term referring to topic or
DM thread. This can help clarify meaning when the term is used in this
specific way.
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.