Fix brunch docs link on the static assets guide (#589)
Fix brunch docs link on the static assets guide (#589)

The documentation was moved out of the main repo, so point the reference to the getting started guide on the website instead.

https://github.com/brunch/brunch/pull/1376
eksperimental/phoenix,eksperimental/phoenix,mobileoverlord/phoenix,phoenixframework/phoenix,jwarwick/phoenix,Joe-noh/phoenix,Joe-noh/phoenix,rafbgarcia/phoenix,jwarwick/phoenix,keathley/phoenix,nshafer/phoenix,optikfluffel/phoenix,0x00evil/phoenix,mitchellhenke/phoenix,0x00evil/phoenix,bsmr-erlang/phoenix,mitchellhenke/phoenix,stevedomin/phoenix,trarbr/phoenix,Gazler/phoenix,michalmuskala/phoenix,dmarkow/phoenix,pap/phoenix,korobkov/phoenix,keathley/phoenix,0x00evil/phoenix,pap/phoenix,gjaldon/phoenix,gjaldon/phoenix,evax/phoenix,dmarkow/phoenix,bratsche/phoenix_guides,Kosmas/phoenix,mschae/phoenix,stevedomin/phoenix,michalmuskala/phoenix,mobileoverlord/phoenix,nshafer/phoenix,Kosmas/phoenix,optikfluffel/phoenix,phoenixframework/phoenix,nshafer/phoenix,trarbr/phoenix,korobkov/phoenix,rafbgarcia/phoenix,Gazler/phoenix,wsmoak/phoenix_guides,optikfluffel/phoenix,evax/phoenix,bsmr-erlang/phoenix,rafbgarcia/phoenix,mschae/phoenix,phoenixframework/phoenix