Add annotation and png Export functionality to CadQuery

[julianstirling]

This issue related to an external project (CAD query) but is necessary for the Nimble Smart Docs

[jmwright]

PNG functionality is on a CadQuery branch here. I will report back when I create a pull request for it. I would like to leave the PR in draft until we have shown that it meets our needs, and then I'll take it out of draft and work with the other core CadQuery devs to get it merged. This way we have two adjacent communities engaged in making sure the export functionality meets a wider range of needs.

[jmwright]

I created a library last year which already has a couple of the features that we've talked about needing for this project. It's called cq-annotate. My thought is that I can just expand that library for this project, but I wanted to post it for discussion.

[julianstirling]

Pushing the end date of this item back as the annotation feature is still evolving as we start to create the renders.

See also the discussion on annotated assembly screenshots: #61