[docs] Support old site's users.html (#5297)

Our Docusaurus 1.x site had a users.html page. This adds a redirect from
that location to /users

website/src/pages/users.html.js

@@ -0,0 +1,7 @@
+import React from 'react';
+import {Redirect} from '@docusaurus/router';
+function Home() {
+    return <Redirect to="/users" />;
+}
+
+export default Home;