webpacker integration does not pull in .css packs

If you require css files in the client_only and client_and_server pack files, they do not get included in the required assets.

Not sure if this is practical or possible. Currently hyper-config pulls in the pack file by doing an opal require on them. But if you try to require a css file it doesnt' like it.

The work around is to add one or both these lines to the layouts, if you are requiring css assets in the pack files:
`<%= stylesheet_pack_tag 'client_only' %>`
If you are requiring css libraries in the `client_only.js` pack file
and
`<%= stylesheet_pack_tag 'client_and_server' %>`
If you are requiring css libraries in the `client_and_server.js` pack file