Updates the help center article to match the style and formatting
of "Import from Slack" and replaces existing content with its
corresponding Markdown macro.
This commit adds functionality to import messages from the
Discussions having direct channels as their parent. As we don't
have topics in the PMs, the messages are imported in interleaved
form in the imported direct channels/PMs.
This was completely unsupported earlier and would have resulted in
an error.