Expose currentLang in getStaticProps param

[willybrauner]

currentLang object is needed in getStaticProps route property to request URL by language

   {
    path: "/article/:slug",
    component: ArticlePage,
    name: "Article",
    getStaticProps: async (props, currentLang) => {
      // props contains route props and params (ex: slug: "article-1")
      const res = await fetch(`https://api.com/posts/${currentLang.key}/${props.params.slug}`);
      const api = await res.json();
      return { api };
    }
  }