Added changelog for version 1.4.0.

Author: jlesage

appdefs.xml

@@ -107,6 +107,13 @@ details.
     </documentation>
     <!-- Changelog of the application. -->
     <history>
+      <release>
+        <version>1.4.0</version>
+        <date>2019-02-24</date>
+        <change>Upgraded Firefox to version 62.0.3-r2.</change>
+        <change>Preferences can now be set via environment variables.</change>
+        <change>Use baseimage based on Alpine Linux 3.9.</change>
+      </release>
       <release>
         <version>1.3.1</version>
         <date>2018-09-18</date>