add external pager support via ES_JSON_PAGER (#65)

pkg/cfg/config.go

@@ -106,6 +106,8 @@ type Config struct {
 
 	FromNode, ToNode             string // cluster reroute move: -f + -t
 	AllowPrimary, AcceptDataLoss bool   // cluster reroute cancel: -p,-a
+
+	Pager string // api repl: -p || PAGER
 }
 
 func NewConfig() *Config {