Add Animation Support for go.Sankey Plots Similar to go.Scatter and go.Bar

Description

I would like to request the addition of animation support for go.Sankey plots, similar to the functionality available in go.Scatter and go.Bar.

Expected Outcome

The go.Sankey plot should have a parameter in the layout for animations, similar to the updatemenus feature. An example of the desired configuration is shown below:

"updatemenus": [{
    "type": "buttons",
    "buttons": [{
        "label": "Your Label",
        "method": "animate",
        "args": [/* Animation arguments here */]
    }]
}]

This feature would allow users to add animations to go.Sankey plots, enhancing their interactivity and visual appeal.

Start by comparing the existing animation support for go.Scatter and go.Bar with the go.Sankey entry point, focusing on how layout updatemenus and the animate method are exposed. Done means go.Sankey accepts the equivalent animation configuration and a regression test or example demonstrates the requested buttons and animation arguments.