Add link to release notes

lib/constants.dart

@@ -43,6 +43,8 @@ const String kFacebookUrl = 'https://www.facebook.com/invoiceninja';
 const String kYouTubeUrl =
     'https://www.youtube.com/channel/UCXAHcBvhW05PDtWYIq7WDFA/videos';
 
+const String kReleaseNotesUrl =
+    'https://github.com/invoiceninja/invoiceninja/wiki/Release-notes';
 const String kDocsUrl = 'https://invoiceninja.github.io/docs';
 const String kDocsCustomDomainUrl =
     'https://invoiceninja.github.io/docs/hosted-custom-domain';

lib/ui/system/update_dialog.dart

@@ -113,7 +113,12 @@ class _UpdateDialogState extends State<UpdateDialog> {
               Navigator.of(context).pop();
             },
           ),
-          if (!account.isUpdateAvailable)
+          if (account.isUpdateAvailable)
+            TextButton(
+              child: Text(localization.releaseNotes.toUpperCase()),
+              onPressed: () => launch(kReleaseNotesUrl),
+            )
+          else
             TextButton(
               child: Text(localization.viewChanges.toUpperCase()),
               onPressed: () => launch(kGitHubDiffUrl.replaceFirst(

lib/utils/i18n.dart

@@ -16,6 +16,7 @@ mixin LocalizationsProvider on LocaleCodeAware {
   static final Map<String, Map<String, String>> _localizedValues = {
     'en': {
       // STARTER: lang key - do not remove comment
+      'release_notes': 'Release Notes',
       'upgrade_to_view_reports': 'Upgrade your plan to view reports',
       'started_tasks': 'Successfully started :value tasks',
       'stopped_tasks': 'Successfully stopped :value tasks',
@@ -74165,6 +74166,10 @@ mixin LocalizationsProvider on LocaleCodeAware {
       _localizedValues[localeCode]['upgrade_to_view_reports'] ??
       _localizedValues['en']['upgrade_to_view_reports'];
 
+  String get releaseNotes =>
+      _localizedValues[localeCode]['release_notes'] ??
+      _localizedValues['en']['release_notes'];
+
   // STARTER: lang field - do not remove comment
 
   String lookup(String key) {