fix light toggle

static/light-toggle.js

@@ -1,5 +1,12 @@
 function themeToggle() {
-  const oldValue = localStorage.getItem('theme');
+  let oldValue = localStorage.getItem('theme');
+  if (!oldValue) {
+    oldValue = 'light';
+    if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+      oldValue = 'dark';
+    }
+  }
+
   let newValue;
   if (oldValue == 'light') {
     newValue = 'dark';