Add rule about forced usage of WebSockets

Author: Bluenix2

pydis_site/templates/events/pages/code-jams/9/rules.html

@@ -12,6 +12,15 @@
 {% block event_content %}
 <ol>
     <li><p>Your solution must use one of the approved frameworks (a list will be released soon). It is not permitted to circumvent this rule by e.g. using the approved framework as a wrapper for another framework.</p></li>
+    <li>
+        <p><strong>Your solution must only communicate through WebSockets</strong>. Any communication between the client and server (or any two server workers), must utilize WebSockets.</p>
+
+        <p>
+            Exceptions to this rule are made for resources such as databases and files, albeit excluding usage other than for storage.
+            For example, you may use PostgreSQL as a database but not its `NOTIFY` command.
+            Lastly, working with subprocesses (through stdin/stdout or <code>multiprocessing.Pool()</code>/<code>concurrent.futures.ProcessPoolExecutor()(</code>) is also exempted from this rule.
+        </p>
+    </li>
     <li><p>Your solution should be platform agnostic. For example, if you use filepaths in your submission, use <code>pathlib</code> to create platform agnostic Path objects instead of hardcoding the paths.</p></li>
     <li>
         <p>