Add a note to setup instructions about 2FA with GitHub (#466)

resolve #465

The instructions on GitHub are pretty clear so hopefully that's good
enough.

_partials/cn/github.md

@@ -5,3 +5,5 @@
 :point_right: **[上传一张照片](https://github.com/settings/profile)** 并在你的GitHub账户中设置你的名称。这一步很重要，因为我们将使用一个带有你头像的内部dashboard。请**现在**立即做这一步，然后再去继续下面的步骤。
 
 ![](images/github_upload_picture.png)
+
+**[启用双因素认证（2FA）](https://docs.github.com/en/authentication/securing-your-account-with-two-factor-authentication-2fa/configuring-two-factor-authentication#configuring-two-factor-authentication-using-text-messages)**。当您尝试登录时，GitHub将向您发送带有代码的短信。这对于安全性很重要，也很快将成为贡献GitHub上的代码的必要条件。

_partials/es/github.md

@@ -5,3 +5,5 @@
 :point_right: **[Sube una foto](https://github.com/settings/profile)** y escribe tu nombre correctamente en tu cuenta GitHub. Esto es importante porque nosotros usaremos un tablero de comando interno con tu avatar. Por favor hazlo **ahora** antes de dar un paso más en esta guía.
 
 ![Foto GitHub](images/github_picture.png)
+
+:point_right: **[Habilita la Autenticación de Dos Factores (2FA)](https://docs.github.com/en/authentication/securing-your-account-with-two-factor-authentication-2fa/configuring-two-factor-authentication#configuring-two-factor-authentication-using-text-messages)**. GitHub te enviará mensajes de texto con un código cuando intentes iniciar sesión. Esto es importante para la seguridad y también pronto será necesario para contribuir código en GitHub.

_partials/fr/github.md

@@ -5,3 +5,5 @@ Est-ce que tu as déjà un compte GitHub ? Si ce n’est pas le cas, [inscris-t
 :point_right: **[Télécharge une photo](https://github.com/settings/profile)** et indique correctement ton nom sur ton compte GitHub. C’est important, car notre tableau de bord interne utilise ton avatar. Fais-le **maintenant** avant de poursuivre la configuration de ton ordinateur.
 
 ![image de GitHub](images/github_picture.png)
+
+:point_right: **[Activez l'authentification à deux facteurs (2FA)](https://docs.github.com/en/authentication/securing-your-account-with-two-factor-authentication-2fa/configuring-two-factor-authentication#configuring-two-factor-authentication-using-text-messages)**. GitHub vous enverra des messages texte avec un code lorsque vous essayez de vous connecter. C'est important pour la sécurité et cela sera bientôt obligatoire pour contribuer du code sur GitHub.

_partials/github.md

@@ -5,3 +5,5 @@ Have you signed up to GitHub? If not, [do it right away](https://github.com/join
 :point_right: **[Upload a picture](https://github.com/settings/profile)** and put your name correctly on your GitHub account. This is important as we'll use an internal dashboard with your avatar. Please do this **now**, before you continue with this guide.
 
 ![GitHub picture](images/github_picture.png)
+
+:point_right: **[Enable Two-Factor Authentication (2FA)](https://docs.github.com/en/authentication/securing-your-account-with-two-factor-authentication-2fa/configuring-two-factor-authentication#configuring-two-factor-authentication-using-text-messages)**. GitHub will send you text messages with a code when you try to log in. This is important for security and also will soon be required in order to contribute code on GitHub.

_partials/pt/github.md

@@ -5,3 +5,5 @@ Você se inscreveu no GitHub? Caso contrário, [faça isso imediatamente](https:
 :point_right: **[Carregue uma imagem](https://github.com/settings/profile)** e coloque seu nome corretamente em sua conta GitHub. Isso é importante porque usaremos um painel interno com seu avatar. Faça isso **agora**, antes de continuar com este guia.
 
 ![Imagem do GitHub](images/github_picture.png)
+
+:point_right: [Ative a Autenticação em Duas Etapas (2FA)](https://docs.github.com/en/authentication/securing-your-account-with-two-factor-authentication-2fa/configuring-two-factor-authentication#configuring-two-factor-authentication-using-text-messages). O GitHub enviará mensagens de texto com um código quando você tentar fazer login. Isso é importante para a segurança e em breve será necessário para contribuir com código no GitHub.