Add new release to front page.

content/_index.html

 ---
 description: Secure messaging, anywhere
 title: Secure messaging, anywhere
-releaseVersion: 1.5.7
-releaseDate: 27 September 2023
+releaseVersion: 1.5.8
+releaseDate: 23 October 2023
 ---
 <div class="intro">
   <ul id="introlist">