chore: add release 10.0 info in about.html (#5492)

ietf/templates/release/about.html

@@ -23,6 +23,7 @@
         moments.  For the nitty-gritty week-to-week code changes, please check the release
         notes or the commit log.
     </p>
+    <h2>Version 10.0.0: Migration to PostgreSQL as the backend database engine</h2>
     <h2>Version 9.0.0: Timezone Aware Data</h2>
     <p>All timestamps in the database are now stored as UTC. Values reported through the API for several 
         models changed, particularly Meeting based models such as TimeSlot where times had previously been
@@ -112,4 +113,4 @@
         of it and its capabilities was made 2002-11-20
         in Atlanta by Thomas Narten.
     </p>
-{% endblock %}
+{% endblock %}