chore(router): set up react router (#5)

- Sets up react router.

[Delivers #161966564]

src/App.js

@@ -1,13 +1,30 @@
 import React, { Component } from 'react';
 import 'semantic-ui-css/semantic.min.css';
+import { BrowserRouter, Route, Switch } from 'react-router-dom';
+
+import Login from './components/Authentication/LoginDummy';
+import Error from './components/ErrorHandlers/MissingPageError';
+import Home from './Home';
 import Header from './components/Header/Header';
 
 class App extends Component {
   render() {
     return (
-      <div className="App">
-        <Header />
-      </div>
+
+      <BrowserRouter>
+        <div>
+          <div className="App">
+            <Header />
+          </div>
+          <Switch>
+            {/* exact looks for the exact path,
+            it prevents the home page from being rendered in all the pages */}
+            <Route path="/" component={Home} exact />
+            <Route path="/login" component={Login} />
+            <Route component={Error} />
+          </Switch>
+        </div>
+      </BrowserRouter>
     );
   }
 }

src/Home.js

@@ -0,0 +1,13 @@
+// This file is temporary for the purpose of testing the routes.
+// It will be deleted as we go on.
+
+import React from 'react';
+
+const Home = () => (
+  <div>
+    <p>This is the dummy landing page.</p>
+    <h1>Welcome to authors haven!!!</h1>
+  </div>
+);
+
+export default Home;

src/components/Authentication/LoginDummy.js

@@ -0,0 +1,9 @@
+import React from 'react';
+
+const Login = () => (
+  <div>
+    <p>This is a dummy login. Welcome!!</p>
+  </div>
+);
+
+export default Login;

src/components/ErrorHandlers/MissingPageError.js

@@ -0,0 +1,9 @@
+import React from 'react';
+
+const Error = () => (
+  <div>
+    <p>Page does not exist.</p>
+  </div>
+);
+
+export default Error;

src/components/Navigation/Navigation.js

@@ -0,0 +1,11 @@
+import React from 'react';
+import { NavLink } from 'react-router-dom';
+
+const Navigation = () => (
+  <div>
+    <NavLink to="/">Home</NavLink>
+    <NavLink to="/login">Login</NavLink>
+  </div>
+);
+
+export default Navigation;