Add content related to basic configuration for DMS package #146

As long as the DMS package is an important package for the users and the grafana documentation can be overwhelming for users who are not used to working with this kind of program, it could be good to have a dedicated space in the documentation for some grafana configurations.
Some content like this one https://forum.dappnode.io/t/begginer-friendly-install-monitoring-system-on-dappnode-using-dms-package/623
, furthermore, it would be interesting adding more information in order to clarify some behaviour of grafana in dappnode like (dappnode/DAppNodePackage-DMS#30)