Programmatically generate SVG (vector) images, animations, and interactive Jupyter widgets

Add link to quick reference

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README.md
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An interactive [Jupyter notebook](https://jupyter.org) widget, `drawsvg.widgets.DrawingWidget`, [is included](#interactive-widget) that can update drawings based on mouse events. The widget does not yet work in Jupyter lab.
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[SVG quick reference docs](https://cduck.github.io/drawsvg/)
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# Install