adopt http-pwa-server

[moebiusmania]

For the deploy strategy we are moving from serving a static page on a simple http server to serving it on a Node.js server, since we need to have a server that:

• supports client-side routing (without hash, see remove hash (#) from routing #16 )
• redirect requests from http to https (see Http redirect to https #4 )
• supports server-side rendering with Puppeteer
• detects bots/spider/crawler request and serve SSR pages (see SSR on bot requests #9 )

and the http-pwa-server module does almost everything of this (except the http redirect part, but we can easily add it).

This are also the reasons why we are moving from the previous proposal of GitHub Pages to Heroku (see #2 ).

On local development the webpack-dev-server is still fine.