Docs[Dashboards]: Create "what to expect in terms of browser memory usage from Grafana"

Currently, we have no guidelines or limitations in the domain of dashboards regarding "what to expect in terms of Grafana browser memory usage". This makes it difficult to answer questions like, "What is considered large dashboards, how many panels, variables? Does performance change when rows or panels are repeated?" ps, I think this documentation will be the first step in opening the conversation about performance in dashboards.