Fix typo in noflash.js.txt (#23)

noflash.js.txt

@@ -2,7 +2,7 @@
 // This will help to prevent a flash if dark mode is the default.
 
 (function() {
-  // Change these if you use sometthing different in your hook.
+  // Change these if you use something different in your hook.
   var storageKey = 'darkMode';
   var classNameDark = 'dark-mode';
   var classNameLight = 'light-mode';