Introduce vega charts

[sverhoeven]

As a C++ developer I would like to learn how to make a (interactive) plot in a web application.

The root finding algorithm returns a single root, which is not enough to plot. We could run it multiple times with different inputs and plot that.

Tasks

• [x] Determine how the root finding algorithm can be use to make a decent/useful plot
• [x] Adjust form to capture required input
• [x] Adjust web worker to generate data for plot
• [x] Use vega to render plot
• [x] Use vega CDN
• [x] Wrap vega in a React component, see example