Fix cookie button.

The button is now implemented via a neat shortcode

layouts/shortcodes/cookie_button.html

@@ -0,0 +1,24 @@
+<!---
+
+Adds a button that, when you click it stores a cookie for the user.
+
+Use as {{< cookie_button cookie_key cookie_value button_text>}}
+-->
+<script>
+function createCookie(name, value, days){
+    var expires;
+    if (days) {
+        var date = new Date();
+        date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
+        expires = "; expires=" + date.toGMTString();
+    }
+    else {
+        expires = "";
+    }
+    document.cookie = name + "=" + value + expires + "; path=/; samesite=strict;";
+}
+</script>
+
+<button onclick="createCookie('{{ index .Params 0}}', '{{ index .Params 1}}', 365)">{{ index .Params 2}}</button>
+
+