Export to JPEG

[openvmp]

Add an option to export models to JPEG file.
Make it very similar to the way PNG is rendered, including moving the work with dependencies into a separate plugin.
All dependencies need to be installed in partcad-cli, but partcad itself should use importlib to check whether the dependencies are available (see how PNG works).

Extend examples/feature_export to render a JPEG file too.

Preferrably, use pure Python dependencies only. Otherwise, after completion create an issue to add another JPEG plugin with pure python dependencies only.