Add release notes mention about strict mode

Change-Id: I93eec041fbccd3961e82f2d7e52d23eb044ec4ea

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

@@ -120,7 +120,8 @@ <h3 id="incompatible">Incompatible or Behavior-altering Changes in @version-mino
             <li>The LoginForm component has been rewritten to better support auto-completion of passwords on modern browsers.
                 Its API, look and DOM structure have changed somewhat, so any application level customizations of LoginForm need changes.
                 See also <a href="http://dev.vaadin.com/ticket/8171">#8171</a></li>
-            <li>The way we handle GWT dependencies has been completely changed. See <a href="#gwtdep">this section</a> for more details</li>
+            <li>The way we handle GWT dependencies has been completely changed. See <a href="#gwtdep">this section</a> for more details.</li>
+            <li>Client side compilation with Maven is now in strict mode by default, failing the compilation on any errors.</li>
         </ul>
         <h3 id="knownissues">Known Issues and Limitations</h3>
         <ul>