Add comment explaining .dockerignore (#4730)
Add comment explaining .dockerignore (#4730)


rafbgarcia/phoenix,optikfluffel/phoenix,nshafer/phoenix,phoenixframework/phoenix,nshafer/phoenix,phoenixframework/phoenix,optikfluffel/phoenix,nshafer/phoenix,0x00evil/phoenix,0x00evil/phoenix,optikfluffel/phoenix,0x00evil/phoenix,rafbgarcia/phoenix,phoenixframework/phoenix,rafbgarcia/phoenix