Add MaterializeCSS styles (#1)

## Changes
* Adds the [AssetPack](https://metacpan.org/pod/Mojolicious::Plugin::AssetPack) Mojolicious plugin
* Adds the [MaterializeCSS](https://www.npmjs.com/package/materialize-css) Node package
* Applies styles to app

Reviewed-on: #1

README.md

@@ -16,10 +16,14 @@ Visit `localhost:3000` with web browser.
 
 ## serve app with local changes
 
-### install dependencies
+### install Mojolicious dependencies
 
     $ docker run --rm -v $PWD:/opt/app --entrypoint carton mojo_app install
 
+### install Node packages
+
+    $ docker run --rm --init -w /opt/mojo_app -v $PWD/mojo_app:/opt/mojo_app node npm install
+
 ### start the server
 
     $ docker run --rm -v $PWD:/opt/app -p 3000:3000 mojo_app