Add note about detection of classic mode apps
Add note about detection of classic mode apps

AlphaStaxLLC/heroku-buildpack-php-custom,Scalingo/php-buildpack,jstacoder/heroku-buildpack-php-1,penciu/apache,nsg/dokku-buildpack-picocms,OKAMca/heroku-buildpack-php,CHH/heroku-buildpack-php,pierredup/packager-buildpack-php,briankilgore/heroku-buildpack-php-prod,Scalingo/php-buildpack,OKAMca/heroku-buildpack-php,stof/heroku-buildpack-php,AlphaStaxLLC/heroku-buildpack-php-custom,stof/heroku-buildpack-php,AlphaStaxLLC/heroku-buildpack-php-custom,mraymond/heroku-buildpack-php,nsg/dokku-buildpack-picocms,cachethq/cachet-buildpack,Jonatasmz/php-buildpack,pierredup/packager-buildpack-php,OKAMca/heroku-buildpack-php,bobmaerten/dokku-buildpack-php,ryosuzuki/php-buildpack,ryosuzuki/php-buildpack,jstacoder/heroku-buildpack-php-1,Jonatasmz/php-buildpack,stof/heroku-buildpack-php,bobmaerten/dokku-buildpack-php,CHH/heroku-buildpack-php,penciu/apache,CHH/heroku-buildpack-php,Scalingo/php-buildpack,penciu/apache,mraymond/heroku-buildpack-php