Feature request: Add Sankey Diagram #457
Description
We should add a Sankey diagram. Matplotlib does have this feature (see here), but it does not look like the more modern format:
What is a Sankey Diagram?
A Sankey diagram is a flow diagram that visualizes how quantities move between stages or categories. The key feature is that the width of each arrow is proportional to the magnitude of the flow, making it easy to see where resources originate, how they split or merge, and where they end up. Sankey diagrams are commonly used to show energy balances, material flows, financial transfers, or process efficiencies, helping highlight dominant pathways and losses at a glance.