Zulip: Add user documentation on stream/topic best practices

[brainwane]

Per #675:

having advice on when you should split a stream into multiple streams, when you should use a new topic vs. replying to an existing one when sending a message, etc., would probably be useful.

This is also the sort of thing that would work well as a tip sent to new users about a month after they join Zulip.

[3ruce]

When I first encountered this aspect of Zulip, I was expecting an option in the attached image to give me the option of splitting a topic off into a new one...

Editing the topic of a message is fine but adding it to the message/topic options might be an idea to increase usability... That might also then reduce the need to send out a new tip after a months time.

[synicalsyntax]

@timabbott Doesn't this already exist in https://chat.zulip.org/help/about-streams-and-topics? If not, how can the current documentation on that page be improved?

[timabbott]

I'm thinking more about the organization level -- how to set up streams in your organization well, what are good naming schemes, when to use a new topic, that you shouldn't put a lot of automated traffic on a human-heavy stream since it's spammy, etc.

[carpecodeum]

do you still need this?