[SwanSpawner] Add message to advertise new Alma9 image with JupyterLab

In the web form when starting a session.

SwanSpawner/swanspawner/templates/options_form_template.html

@@ -1,5 +1,6 @@
 <style> .nb{ font-weight:normal } </style>
 <style> .nbs{ font-weight:normal; font-size:small } </style>
+<style> .news{ font-weight:normal; background-color:yellow } </style>
 <script type="text/javascript">
 <!--
 
@@ -176,6 +177,9 @@
     <label for="placeholder">
     <span class='nb' id="optionsHeader">Specify the configuration parameters for the SWAN container that will be created for you.</span>
     </label>
+    <label for="alma9">
+    <span class='news' id="alma9">Select <b>AlmaLinux 9</b> as Platform to try out our new experimental Alma9 image with <b>JupyterLab</b> as default interface! More information <a target="_blank" href="https://swan.docs.cern.ch/alma9/">here</a>.</span>
+    </label>
     <br><br>
     <label for="lcgReleaseOptions">Software stack <a href="#" onclick="toggle_visibility('lcgReleaseDetails');"><span class='nbs'>more...</span></a>
     <div style="display:none;" id="lcgReleaseDetails">