Add generation of SVG image with latest jar version

When querying group-id/artifact-id/latest-version.svg, an SVG image is created that contains the latest version of the library and can be embedded into web pages.

Example of such image: https://hatchery.bytopia.org/clojars/lein-droid.svg

I ported my script straightforwardly, and also the image. I don't pretend to understand design, so the image template is not final (can be changed up to you).