[docs] add enable-gcm
[docs] add enable-gcm

nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,kurainooni/nw.js,nwjs/nw.js,kurainooni/nw.js,kurainooni/nw.js,kurainooni/nw.js,nwjs/nw.js,kurainooni/nw.js,kurainooni/nw.js,nwjs/nw.js,kurainooni/nw.js