Update adding_pages.md (#3546)
Update adding_pages.md (#3546)

Source code doesn't have brackets
optikfluffel/phoenix,eksperimental/phoenix,phoenixframework/phoenix,jwarwick/phoenix,phoenixframework/phoenix,keathley/phoenix,0x00evil/phoenix,michalmuskala/phoenix,keathley/phoenix,rafbgarcia/phoenix,0x00evil/phoenix,nshafer/phoenix,phoenixframework/phoenix,eksperimental/phoenix,optikfluffel/phoenix,nshafer/phoenix,rafbgarcia/phoenix,optikfluffel/phoenix,michalmuskala/phoenix,0x00evil/phoenix,jwarwick/phoenix,nshafer/phoenix,rafbgarcia/phoenix