Testing SKAMPI documentation

A new section/page has been added titled Testing SKAMPI intended to house information about testing and verifying the SKAMPI prototype. The subsection Testing Infrastructure as Code provides an overview of why and how to test the SKAMPI infrastructure configuration, i.e. Helm charts. It's mostly summarising the work done accomplished in !19 (merged) and !22 (merged)

Once this is reviewed and merged, I would like to link it directly from the SKA Developer's portal documentation.