Extract language from `html` instead of browser UI

Extensions/UserScript/Return Youtube Dislike.user.js

@@ -289,7 +289,7 @@ function roundDown(num) {
 }
 
 function numberFormat(numberState) {
-  const userLocales = navigator.language;
+  const userLocales = document.documentElement.lang;
 
   const formatter = Intl.NumberFormat(userLocales, {
     notation: "compact",
@@ -369,4 +369,4 @@ if (isMobile) {
   setInterval(() => {
     getDislikeButton().querySelector(".button-renderer-text").innerText = mobileDislikes;
   }, 1000);
-}
+}