Added additional information about the exsiting metrics exporter for Prometheus monitoring system based on libipmctl to the README.md file
Added additional information about the exsiting metrics exporter for Prometheus monitoring system based on libipmctl to the README.md file

Signed-off-by: Karol Zmijewski <41ac0dbec76bf3b50d01af716a438f2ccacb087f@gmail.com>

intel/ipmctl,intel/ipmctl,intel/ipmctl,intel/ipmctl