insights: design for insights on the search screen

Created by: Joelkw

We need quick designs for https://github.com/sourcegraph/sourcegraph/issues/38440 .

We likely want 1 state where the graph is not visible (a % change or some other indicator) and 1 where it is. It's likely we can work within the system / prototype structure @benvenker set up here long term, but we can't wait for it (e.g., we may also need quick designs to ship within our existing UI).