Mention scss cache in release notes (#15228)

Change-Id: I1b0fc70632d82e7a656cdc61f00a75dda3cc316c

WebContent/release-notes.html

@@ -114,7 +114,8 @@
             <li>@Viewport annotation for declaratively defining a mobile viewport definition for a UI.</li>
             <li>Component captions, TabSheet/Accordion tab captions and Calendar event captions can be configured to be displayed as HTML.</li>
             <li>Selects use converters when presenting itemids.</li>
-            <li>Improved performance when server response contains no visual changing (e.g. empty polling responses).</li>
+            <li>Improved performance when server response contains no visual changes (e.g. empty polling responses).</li>
+            <li>Development time on-the-fly scss compilation cache may now be preserved when redeploying or restarting the server.</li>
             <li>Unified JSON library for using the same API in both server-side and client-side code.</li>
             <li>Range validators and converters for additional numerical types.</li>
             <li>Support for fine grained add/remove item events in in-memory containers.</li>