Describe some example use cases in the README

[joellabes]

The README dives into the weeds pretty quickly in terms of how to configure the package, but it doesn't actually spend much time talking about what problems it solves. When I link people to it, I feel like they might not have anything to grab onto and grok the purpose.

The list of models isn't immediately actionable - maybe if it contained example interesting columns and a couple of descriptions of the sorts of things you could do with them? E.g. the fct_dbt__model_executions model has total_node_runtime and rows_affected or fct_dbt__test_executions has every test and whether it passed/failed/errored out and in how long.