Update copyright years

index.html

@@ -3,7 +3,7 @@
  Copyright (c) 2016 Mikhail Maximov
  vigorous.activity at gmail dot com
 
- Copyright (c) Antony Polukhin, 2021-2022
+ Copyright (c) Antony Polukhin, 2021-2023
 
  Distributed under the Boost Software License,
  Version 1.0. (See accompanying file LICENSE_1_0.txt
@@ -31,7 +31,7 @@
     <a href="https://www.boost.org/doc/libs/master/doc/html/conversion.html">https://www.boost.org/doc/libs/master/doc/html/conversion.html</a>
   </p>
   <p>
-    &copy; Antony Polukhin, 2014-2022
+    &copy; Antony Polukhin, 2014-2023
   </p>
 </body>
 </html>