help-docs: Move help center documentation to top level directory.

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.

help/typing-notifications.md

@@ -0,0 +1,30 @@
+# Typing notifications
+
+Zulip displays typing notifications when viewing a private message or
+group private message conversation to which one of the other
+participants is currently composing a message.
+
+Typing notifications are only sent while one is actively editing text
+in the compose box, and they disappear if typing is paused for about
+15 seconds.  Just having the compose box open will not send a typing
+notification.
+
+### Disable typing notifications
+
+If you'd prefer that others not know whether you're typing, you can
+configure Zulip to not send typing notifications.
+
+{start_tabs}
+
+{settings_tab|account-and-privacy}
+
+1. Under **Privacy**, toggle **Let recipients see when I'm typing
+   private messages**.
+
+{end_tabs}
+
+## Related articles
+
+* [Private messages](/help/private-messages)
+* [Status and availability](/help/status-and-availability)
+* [Read receipts](/help/read-receipts)