Update version number from v6.0 to v6.1.5

Author: ravindu644

index.html

@@ -77,7 +77,7 @@
   <section class="hero">
     <div class="hero-inner">
       <div>
-        <div class="hero-badge"><span></span>v6.0 · Open Source</div>
+        <div class="hero-badge"><span></span>v6.1.5 · Open Source</div>
         <h1>
           Linux containers<br>
           on
@@ -545,4 +545,4 @@ <h2>Ready to run real containers?</h2>
   </script>
 </body>
 
-</html>
+</html>