Add FAQ on using package.engines...
Add FAQ on using package.engines...

...mentioning @Spown's comment on #25
LTWS/OpenShift-Nodejs-LTS,JonasHavers/openshift-cartridge-nodejs,joseph-turner/openshift-cartridge-nodejs,icflorescu/openshift-cartridge-nodejs,joseph-turner/openshift-cartridge-nodejs,joseph-turner/openshift-cartridge-nodejs,icflorescu/openshift-cartridge-nodejs,JonasHavers/openshift-cartridge-nodejs,LTWS/OpenShift-Nodejs-LTS,LTWS/OpenShift-Nodejs-LTS,JonasHavers/openshift-cartridge-nodejs,icflorescu/openshift-cartridge-nodejs