Consider replacing Chart.js with a native SVG plotting library

[gflegar]

As already discussed in #8, since Chart.js uses a canvas to output the data (raster graphics), it extremely difficult (if not impossible) to get it to output vector graphics such as SVG which would be useful to be able to include high quality (and reasonably compressed) plots generated by GPE into scientific papers.

One option would be to explore the possibility of replacing Chart.js with a different library that generates SVG natively. One example is Chartist. There are more examples of various plotting libraries in this article, not all with SVG capabilities.

Of course, one consideration needs to be the integration between Jsonata and the new library, i.e. can a JSON object be converted into the input for the new library with reasonable effort?

Also, using a different library would mean we need to convert all existing plotting scripts to output the result in the new format.