Provide dataset context on the chart creation (explore) experience

As a user, when I go to build a chart from a dataset, it would be super helpful to have a quick way to view what is in the data set while staying in context.

Current Behavior - I select a dataset and visualization, and then end up on Explore screen which has no data in the data section. This means I need to either leave this screen to go to SQL lab to explore the dataset or I need to select a metric and then view the data set.

Proposed Solution:

There would be another tab here that would be the first thing I see when I load this screen that shows me everything in the dataset (as if I explored the dataset in SQL Lab).

I can then use this information to help me create filters, select my metric, build formulas, etc without having to leave.