add simplified Chinese translation (75%)

src/css/icons.scss

@@ -27,7 +27,7 @@ $icons: notification_saved, notification_success, notification_upgrade;
     }
 }
 
-$languages: en, de, cs, da, et, es-419, fr, it, pt-BR, sv, tr, el, ru, uk, zh-TW, nb, mt-MT, ar, nl, vi, th,
+$languages: en, de, cs, da, et, es-419, fr, it, pt-BR, sv, tr, el, ru, uk, zh-TW, zh-CN, nb, mt-MT, ar, nl, vi, th,
     hu, pl, ja, kor, no, pt-PT;
 
 @each $language in $languages {

src/js/languages.js

@@ -80,4 +80,10 @@ export const LANGUAGES = {
         code: "no",
         region: "",
     },
+    "zh-CN": {
+        name: "简体中文",
+        data: require("./built-temp/base-zh-CN.json"),
+        code: "zh",
+        region: "CN",
+    },
 };