[Feature] Support SVG use objects

[Sophist-UK]

Also known in Inkscape as clones.

Use objects take a reference to an SVG element and use it as a new object, applying a transform (size, rotation, mirror etc.).

Currently Deepnest ignores clones, whereas it should ideally respect clones and their transforms and treat them as SVG objects.

[bosd]

Deepnest is abondoned by the original author.
There is a community based fork at this repo: https://github.com/deepnest-io/Deepnest