feat: implement login / logout through GitHub

this fixes #89

src/component/data/firebase.js

@@ -12,3 +12,5 @@ const firebaseConfig = {
 
 firebase.initializeApp(firebaseConfig)
 export const db = firebase.firestore()
+export const auth = firebase.auth();
+export const GitHubProvider = new firebase.auth.GithubAuthProvider()

src/component/top-menu/top-menu.component.jsx

@@ -1,19 +1,41 @@
-import React from 'react'
+import React, { useState } from 'react'
 import { StyledTopMenu, StyledLink, StyledButton } from './top-menu.style'
 import { WebInfoState } from '../web-info/web-info.context';
+import { auth, GitHubProvider } from '../data/firebase';
 
 const TopMenu = () => {
   const { toggleChat, updateToggleChat } = WebInfoState()
+  const [ loggedIn, setLoggedIn ] = useState(false) 
 
   const handleToggleChat = () => {
     updateToggleChat({ type: 'TOGGLE_CHAT' });
   }
 
+  const handleLogInAndOut = () => {
+    if (loggedIn) {
+      auth.signOut();
+    }
+    else {
+      auth
+        .signInWithPopup(GitHubProvider)
+        .then(user => {
+          console.log(user)
+        })
+        .catch(error => {
+          console.error(error)
+        })
+    }
+  }
+
+  const getLogInOutLabel = () => loggedIn ? 'Ba Bye' : 'Let me in!'
+
   return (
     <StyledTopMenu>
       <StyledLink to="/">Home</StyledLink>
       <StyledLink to="/dashboard">Dashboard</StyledLink>
-      <button>Log in</button>
+      <button onClick={handleLogInAndOut}>
+        {getLogInOutLabel()}
+      </button>
       <StyledButton onClick={handleToggleChat}>{
         toggleChat ? 'Invizi Chat' : 'Gimme chat now!'
       }</StyledButton>