Add ORaaS in section "Who is using it?"

index.html

@@ -51,7 +51,16 @@ layout: home_orekit
   <div class="col-sm-12 col-md-6 col-lg-4 col-xl-4">
 
     <h1>Who is using it?</h1>
+
     <ul class="fa-ul">
+
+      <li><span class="fa-li fa-lg fa fa-gears"></span>
+        <p><a href="https://uk.c-s.fr/">CS Group</a> develops
+          <a href="https://oraas.orekit.space">ORaaS</a> (Orekit-as-a-Service),
+          an Orekit-based web service including demos, tools and a REST API to
+          access services such as orbit determination.</p>
+      </li>
+
       <li><span class="fa-li fa-lg fa fa-gears"></span>
         <p><a href="https://www.airbus.com/space.html">Airbus Defence and Space</a>
           (ADS) uses Orekit in
@@ -104,6 +113,7 @@ layout: home_orekit
           <a href="https://www.orekit.org/news/2017/12/01/orekit-day-2017-presentations.html">Orekit Day 2017</a> and
           <a href="https://www.orekit.org/news/2019/05/28/orekit-day-2019-presentations-and-first-impressions.html">Orekit Day 2019</a>.</p>
       </li>
+
     </ul>
 
   </div>