add option to add "select" mode on any figure (specifically, Heatmap)

從 go.FigureWidget 範例開始，聚焦於 issue 中描述的 layout.dragmode、modebar 選項，以及 go.Heatmap 互動。檢查當圖表只包含 Heatmap 時，選取回呼和選取邊界是如何提供的。完成的標準是：無需加入虛設的 go.Scatter，即可透過 modebar 在 pan 或 zoom 與 select 之間切換。

It doesn't seem possible to add a "select" dragmode to a figure with a go.Heatmap object. You can specify the starting dragmode as "select", in which case you can immediately drag and select. But if I wanted to pan, I can't choose to select afterwards. I cannot add it to the modebar. I would like to be able to do this so I can select a region of interest on my heatmap, and setup a callback to set this region of interest in my code. I don't care about actually selecting the points in the heatmap, just the bounds of the selection box.

My workaround to this is to add a go.Scatter to my figure:

layout =  go.Layout(
        showlegend=False,
        autosize=False,
        xaxis=dict(
            showgrid=False,
            zeroline=False,
            visible=False,
            range=[0, images.shape[2] - 1],
        ),
        yaxis=dict(
            showgrid=False,
            zeroline=False,
            visible=False,
            range=[images.shape[1] - 1, 0],
            scaleanchor="x",
            scaleratio=1,
        ),
        dragmode="zoom",
        modebar=go.layout.Modebar(remove=["lasso"]),
    )

heat = go.FigureWidget(
    data=[
        go.Scatter(
            x=[0],
            y=[0],
        ),
        go.Heatmap(z=current_image, colorscale="Viridis"),
    ],
    layout=layout,
)

This works, but is kind of silly...