Emit selection events in drawmode when an existing selection modified

[archmoj]

When a selection modified, selection events should be emitted in various drag modes i.e. including shape drawing modes,
like the example below:

Plotly.newPlot(gd, {"data": [{y: [1, 2, 3]}], "layout": {
    "dragmode": "drawrect",
    "selections": [{ x0: 0.5, x1: 1.5, y0: 1.5, y1: 2.5}]
}})

gd.on('plotly_selected', function(data) { console.log(data); });

Right now the v2.13.1 does not emit such events.
This PR fixes this bug.

@plotly/plotly_js

[alexcjohnson]

💃