feat(pxe): add a section about the console arg
feat(pxe): add a section about the console arg

ionave/docs,coreos/docs,endocode/coreos-docs,bq-xiao/docs,wli6/docs,atxwebs/docs,skynet/docs,hkjn/docs-1,jdloft/docs,michelleN/docs,joshix/docs,mjg59/docs,mischief/coreos-docs,robszumski/docs,iankronquist/docs,jonboulle/docs,ksmaheshkumar/docs-2,marineam/coreos-docs