Enable SSR for HelloWorld

1. Turn on prerender: true so component server renders, viewable
   the "view page source" for http://localhost:3000/hello_world
2. React on Rails config needs to set for using the same bundle
   for client and server rendering.
3. Due to the rails/webpacker importing the HMR: true and inline: true
   in v5.1, we need to disable those.
4. We can only run this using the
   foreman start -f Procfile.dev
   because HMR will not work with SSR until we have a separate bundle for
   SSR.

app/views/hello_world/index.html.erb

@@ -1,2 +1,2 @@
 <h1>Hello World</h1>
-<%= react_component("HelloWorld", props: @hello_world_props, prerender: false) %>
+<%= react_component("HelloWorld", props: @hello_world_props, prerender: true) %>

config/initializers/react_on_rails.rb

@@ -42,4 +42,6 @@
   # React components.
   #
   config.server_bundle_js_file = "hello-world-bundle.js"
+
+  config.same_bundle_for_client_and_server = true
 end

config/webpacker.yml

@@ -60,9 +60,9 @@ development:
     host: localhost
     port: 3035
     public: localhost:3035
-    hmr: true
+    hmr: false
     # Inline should be set to true if using HMR
-    inline: true
+    inline: false
     overlay: true
     compress: true
     disable_host_check: true