contributor docs: Add guidelines on moderating the Zulip community.

CODE_OF_CONDUCT.md

@@ -102,3 +102,71 @@ This Code of Conduct is adapted from the
 under a
 [Creative Commons BY-SA](https://creativecommons.org/licenses/by-sa/4.0/)
 license.
+
+## Moderating the Zulip community
+
+Anyone can help moderate the Zulip community by helping make sure that folks are
+aware of the [community guidelines](https://zulip.com/development-community/)
+and this Code of Conduct, and that we maintain a positive and respectful
+atmosphere.
+
+Here are some guidelines for you how can help:
+
+- Be friendly! Welcoming folks, thanking them for their feedback, ideas and effort,
+  and just trying to keep the atmosphere warm make the whole community function
+  more smoothly. New participants who feel accepted, listened to and respected
+  are likely to treat others the same way.
+
+- Be familiar with the [community
+  guidelines](https://zulip.com/development-community/), and cite them liberally
+  when a user violates them. Be polite but firm. Some examples:
+
+  - @user please note that there is no need to @-mention @\_**Tim Abbott** when
+    you ask a question. As noted in the [guidelines for this
+    community](https://zulip.com/development-community/):
+
+    > Use @-mentions sparingly… there is generally no need to @-mention a
+    > core contributor unless you need their timely attention.
+
+  - @user, please keep in mind the following [community
+    guideline](https://zulip.com/development-community/):
+
+    > Don’t ask the same question in multiple places. Moderators read every
+    > public stream, and make sure every question gets a reply.
+
+    I’ve gone ahead and moved the other copy of this message to this thread.
+
+  - If asked a question in a PM that is better discussed in a public stream:
+    > Hi @user! Please start by reviewing
+    > https://zulip.com/development-community/#community-norms to learn how to
+    > get help in this community.
+
+- Users sometimes think chat.zulip.org is a testing instance. When this happens,
+  kindly direct them to use the **#test here** stream.
+
+- If you see a message that’s posted in the wrong place, go ahead and move it if
+  you have permissions to do so, even if you don’t plan to respond to it.
+  Leaving the “Send automated notice to new topic” option enabled helps make it
+  clear what happened to the person who sent the message.
+
+  If you are responding to a message that's been moved, mention the user in your
+  reply, so that the mention serves as a notification of the new location for
+  their conversation.
+
+- If a user is posting spam, please report it to an administrator. They will:
+
+  - Change the user's name to `<name> (spammer)` and deactivate them.
+  - Delete any spam messages they posted in public streams.
+
+- We care very much about maintaining a respectful tone in our community. If you
+  see someone being mean or rude, point out that their tone is inappropriate,
+  and ask them to communicate their perspective in a respectful way in the
+  future. If you don’t feel comfortable doing so yourself, feel free to ask a
+  member of Zulip's core team to take care of the situation.
+
+- Try to assume the best intentions from others (given the range of
+  possibilities presented by their visible behavior), and stick with a friendly
+  and positive tone even when someone‘s behavior is poor or disrespectful.
+  Everyone has bad days and stressful situations that can result in them
+  behaving not their best, and while we should be firm about our community
+  rules, we should also enforce them with kindness.