feat: add darkmode on userpreference

Author: schmelto

src/demo/js/toggle-dark.js

@@ -1,8 +1,10 @@
 const icon = document.querySelector(".darkmode i");
-if (window.matchMedia("(prefers-color-scheme: dark)").matches == true) {
-  darkmode();
-} else {
-  lightmode();
+if (getCookie("darkmode") === null) {
+  if (window.matchMedia("(prefers-color-scheme: dark)").matches == true) {
+    darkmode();
+  } else {
+    lightmode();
+  }
 }
 
 function toggleTheme() {
@@ -33,3 +35,20 @@ function setCookie(cname, cvalue, exdays) {
   var expires = "expires=" + d.toUTCString();
   document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
 }
+
+function getCookie(name) {
+  var dc = document.cookie;
+  var prefix = name + "=";
+  var begin = dc.indexOf("; " + prefix);
+  if (begin == -1) {
+    begin = dc.indexOf(prefix);
+    if (begin != 0) return null;
+  } else {
+    begin += 2;
+    var end = document.cookie.indexOf(";", begin);
+    if (end == -1) {
+      end = dc.length;
+    }
+  }
+  return decodeURI(dc.substring(begin + prefix.length, end));
+}