Make cookie secure by default

Change-Id: I1090977d9ca16106f8afa2b4c0298bc830e11782
diff --git a/cmd/koralmapper/static/config.js b/cmd/koralmapper/static/config.js
index a5f9a6c..9234d78 100644
--- a/cmd/koralmapper/static/config.js
+++ b/cmd/koralmapper/static/config.js
@@ -35,7 +35,7 @@
 
   function writeCookie(state) {
     var value = encodeURIComponent(JSON.stringify(state));
-    document.cookie = cookieName + "=" + value + "; path=/; SameSite=Lax; max-age=31536000";
+    document.cookie = cookieName + "=" + value + "; path=/; SameSite=Lax; Secure; max-age=31536000";
   }
 
   function deleteCookie() {