Add config docs for file discovery
Add config docs for file discovery

chosenken/docs,du2016/prometheus-docs,chosenken/docs,fabxc/docs,ChaoticMind/docs,dato/prometheus-docs,ddfreyne/prometheus-docs,pdbogen/docs,Cepave/openfalcon.io,prometheus/docs,jmptrader/docs,dln/docs,pdbogen/docs,jmptrader/docs,prometheus/docs,Cepave/openfalcon.io,fabxc/docs,tcolgate/docs,ChaoticMind/docs,jimmidyson/docs,evanphx/docs,prometheus/docs,Cepave/openfalcon.io,bluecmd/prometheus-docs,du2016/prometheus-docs,bluecmd/prometheus-docs,chosenken/docs,dln/docs,vic3lord/docs,dln/docs,open-falcon/open-falcon.github.io,ddfreyne/prometheus-docs,chosenken/docs,jimmidyson/docs,tcolgate/docs,evanphx/docs,ChaoticMind/docs,evanphx/docs,open-falcon/open-falcon.github.io,tcolgate/docs,jmptrader/docs,dato/prometheus-docs,du2016/prometheus-docs,open-falcon/open-falcon.github.io,ddfreyne/prometheus-docs,ddfreyne/prometheus-docs,jimmidyson/docs,vic3lord/docs,fabxc/docs,bluecmd/prometheus-docs,vic3lord/docs,dato/prometheus-docs,pdbogen/docs