Update the detect script to support publishconf.py
Update the detect script to support publishconf.py

Related to #2

pyladies-brazil/heroku-buildpack-pelican,wics-uw/heroku-buildpack-pelican,ipartola/heroku-buildpack-pelican,Girbons/buildpack-mkdocs,Girbons/buildpack-mkdocs,ipartola/heroku-buildpack-pelican,getpelican/heroku-buildpack-pelican,wics-uw/heroku-buildpack-pelican,ckcollab/heroku-buildpack-pelican,ronert/heroku-buildpack-pelican,pyladies-brazil/heroku-buildpack-pelican,thedotpost/heroku-buildpack-pelican,tpmanley/heroku-buildpack-pelican,ronert/heroku-buildpack-pelican,ckcollab/heroku-buildpack-pelican,thedotpost/heroku-buildpack-pelican,tpmanley/heroku-buildpack-pelican,getpelican/heroku-buildpack-pelican