PMM-7 add initail docs (#1499)
PMM-7 add initail docs (#1499)

* PMM-7 add initail docs

* Update pmm/README.md

Co-authored-by: Alex Tymchuk <ca2ef7b7b2fa0df38af37caba9edccf94c142988@percona.com>
Percona-Lab/jenkins-pipelines,Percona-Lab/jenkins-pipelines,Percona-Lab/jenkins-pipelines,Percona-Lab/jenkins-pipelines