Add chapters to the doc at https://foshttpcache.readthedocs.io/en/latest/proxy-configuration.html to explain how to set up fastly resp cloudflare to work with FOSHttpCache.
lets not make general fastly and cloudflare tutorials, but explain only things specific for FOSHttpCache, like the fastly vcl for cache tags and such (that is probably quite similar to the varnish proxy configuration chapter)