feat(translate): add Spanish (es) translations for single-page UI

html/login.html

@@ -83,7 +83,8 @@ button:hover{filter:brightness(1.1)}
   var L={
     en:["Switch Login","RTLPlayground management interface","Password","Sign in","Wrong password, try again."],
     ja:["スイッチ ログイン","RTLPlayground 管理インターフェース","パスワード","ログイン","パスワードが違います。もう一度お試しください。"],
-    zh:["交换机登录","RTLPlayground 管理界面","密码","登录","密码错误，请重试。"]
+    zh:["交换机登录","RTLPlayground 管理界面","密码","登录","密码错误，请重试。"],
+    es:["Inicio de sesión del switch","Interfaz de gestión de RTLPlayground","Contraseña","Iniciar sesión","Contraseña incorrecta, inténtalo de nuevo."]
   };
   var l=null;
   try{l=localStorage.getItem("rtl_lang");}catch(e){}