utility to export svg into html image

[mwdchang]

Summary

Adds utility functions to convert SVG into image.

This is not in use for now as where we want to apply SVG=>Image transform (model-diagram), it requires CSS style adjustments and tweaks to the governing logic that are probably better off as a separate PR.

Testing

You add the this to the end of renderGraph() function in tera-model-diagram.vue to test, it appends the image(s) onto the document body. The image(s) are not 100% faithful because of the aforementioned style changes that are not carried over when converting to an image.

     const imageTest = await svgToImage(graphElement.value?.querySelector('svg') as any);
     document.body.appendChild(imageTest);

[mwdchang]

Blob URL doesn't seem to work well with node, so no unit test for this one.

[blanchco]

okay!

[shawnyama]

cool