include vw as simplify algorithm including in the widget

[mattijn]

The simplify_algorithm listens to vw for Visvalingam-Whyatt and dp for Douglas-Peucker. Defaults to dp.
This is now also included in the to_widget().

import geopandas
import topojson

data = geopandas.read_file(geopandas.datasets.get_path("naturalearth_lowres"))
data = data[(data.continent == "North America")]

tj = topojson.Topology(data)
tj.to_widget()

See gif: