Added 404, error and test sender page

src/pages/_error.js

@@ -0,0 +1,29 @@
+function Error ({ statusCode }) {
+  const render404 = () => {
+    return (
+      <center>
+        <h1>404</h1>
+        <iframe width='100%' height='465' src='https://www.youtube-nocookie.com/embed/GOzwOeONBhQ' frameborder='0' allow='accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture' allowfullscreen />
+      </center>
+    )
+  }
+
+  if (statusCode === 404) {
+    return render404()
+  } else {
+    return (
+      <p>
+        {statusCode
+          ? `An error ${statusCode} occurred on server`
+          : 'An error occurred on client'}
+      </p>
+    )
+  }
+}
+
+Error.getInitialProps = ({ res, err }) => {
+  const statusCode = res ? res.statusCode : err ? err.statusCode : 404
+  return { statusCode }
+}
+
+export default Error