Add PricePlow to README
Add PricePlow to README

claylo/api-docs,ProcessOut/documentation,Ibercheck/api-docs,linchpinio/docs,ProcessOut/documentation,Ibercheck/api-docs,ProcessOut/documentation,linchpinio/docs,bookiza/docs,linchpinio/docs,claylo/api-docs,claylo/api-docs,bookiza/docs,Ibercheck/api-docs,bookiza/docs,kasko/docs,bookiza/docs