updates css cache reference

Author: Paul Savoie

docs/_includes/header.html

@@ -36,7 +36,7 @@
   <meta name="description" content="{{description}}"/>
   <!-- End Jekyll SEO tag -->
   <link rel='stylesheet' href='/assets/css/hint.min.css'>
-  <link rel="stylesheet" href="/assets/css/index.css?cache=2025-04-25">
+  <link rel="stylesheet" href="/assets/css/index.css?cache=2025-05-15">
   <link rel="alternate" type="application/atom+xml" title="SignPath.io Blog" href="/feed.xml">
   <script src='/assets/index.js?cache=2024-12-18'></script>
   <script src='/assets/js/main-bundle.js?cache=2025-03-06'></script>