Update release note to mention Java 11 support (#11697)

* Update release note to mention Java 11 support

* Update explanation about client side code

all/src/main/templates/release-notes.html

@@ -337,9 +337,10 @@
         <h2 id="supportedversions">Supported Technologies</h2>
 
         <p>
-            Vaadin Framework 8 is compatible with <b>Java 8 and 9</b>. 
+           The server-side Vaadin Framework 8 is compatible with <b>Java 8 and 11</b>. Note, that the client-side Java code, compiled using GWT to be run as JS on the browser side, only supports language features up to Java 9 and a subset of JDK libraries. 
 	Vaadin Framework 8 is developed and tested with Oracle JDK, but other
-		compliant Java distributions should work as well. Vaadin Framework
+		compliant Java distributions should work as well. More about Java support in <a href="https://vaadin.com/faq">
+            FAQ</a>. Vaadin Framework
             8 is especially supported on the following <b>operating
                 systems</b>:
         </p>