Give credit to the new theme

Author: hartwork

index.htm

@@ -447,7 +447,7 @@ <h2 class="display-4">Upcoming Release</h2>
     </div><!-- jumbotron -->
 
     <p>
-      A small handy tool developed by <a href="https://blog.hartwork.org/">Sebastian Pipping</a> in 2021 using Bootstrap 4 and jQuery.<br/>
+      A small handy tool developed by <a href="https://blog.hartwork.org/">Sebastian Pipping</a> in 2021 using <a href="https://bootswatch.com/4/united/">Bootswatch 4 United</a> and jQuery.<br/>
       If you like it, please support it by starring the <a href="https://github.com/hartwork/shared-library-version-bump">GitHub repository</a>. Thank you!
     </p>
     <p>