docs: ✨ display styled pages when signIn and unauthorized

Signed-off-by: slumbering <slumbering.pierrot@gmail.com>

website/src/components/DocPageAuthentication.js

@@ -0,0 +1,13 @@
+import React from "react";
+import { GithubLoginButton } from 'react-social-login-buttons';
+import style from './DocPageAuthentication.module.css'
+
+export default function DocAuthentication() {
+    return (
+        <div className={style.container}>
+            <h1 className={style.h1}>Welcome on Dagger documentation</h1>
+            <p>Please Sign in to Github in order to get access to the doc</p>
+            <GithubLoginButton className={style.btn__github} onClick={() => window.location.href = `//github.com/login/oauth/authorize?client_id=${process.env.REACT_APP_CLIENT_ID}&scope=user&allow_signup=false`} />
+        </div>
+    )
+}