add creative commons license

Author: wkelsey-apple

smith_chart/index.html

@@ -501,7 +501,10 @@ <h4>Let me know of any issues or requests!</h4>
     <div class="container-xl">
       <div class="row mt-2">
         <div class="col">
-          Copyright &copy; Will Kelsey <span id="current-year"></span>. www.will-kelsey.com/smith_chart
+          © <span id="current-year"></span> Will Kelsey. This work is licensed under a  
+        <a rel="license" href="https://creativecommons.org/licenses/by/4.0/" target="_blank">
+            Creative Commons Attribution 4.0 International License
+        </a>.
           <script>
             document.getElementById("current-year").textContent = new Date().getFullYear();
         </script>