Update web pages.

Author: Kasper Peeters

web2/cadabra2/source/download.html

@@ -118,6 +118,20 @@ <h2>Binary packages</h2>
     </div>
   </div>
 
+  <div class="distrotype">
+    <img src="static/images/docker-logo-blue.svg"/>
+    <div class="distrotxt">
+      If you only want to use Cadabra from within Jupyter, you can use
+      the <a href="https://hub.docker.com/r/kpeeters/cadabra2-jupyter">official
+      Docker image at DockerHub</a>. This container exposes the
+      Jupyter server on a local URL which you can access using your
+      browser, and stores notebooks in your home directory. Available
+      for both AMD64 and ARM64 architectures. Be aware that you will
+      miss out on some of the goodies of the Cadabra notebook
+      interface.
+    </div>
+  </div>
+
   <div class="distrotype">
     <img src="static/images/apple_logo.png"/>
     <div class="distronum">macOS</a></div>

web2/cadabra2/source/jupyter.html

@@ -42,7 +42,18 @@ <h2>Installation</h2>
   to <a href="faq.html#q_01_01">adjust your <tt>PYTHONPATH</tt></a>.
 </p>
 
-<!--<h2>Old Xeus-based kernel</h2>
+<h2>Docker version</h2>
+<p class="hyphenate">
+  Alternatively, you can use
+  the <a href="https://hub.docker.com/r/kpeeters/cadabra2-jupyter">official
+  Docker image for Cadabra</a>, available from DockerHub, which
+  contains a Jupyter server with the Cadabra kernel. This will not be
+  able to see existing Python package installations on your system,
+  but has the advantage of being easy to install (and easy to remove,
+  if you ever want to do that).
+</p>
+
+  <!--<h2>Old Xeus-based kernel</h2>
 <p>
   To obtain the Cadabra kernel for Jupyter, you need to either install
   it from Anaconda,