This helper tool uses BBEdit's Preview Windows to preview Markdown syntax in your rustdocs. It has the following components:
- A binary Preview Filter
- The source for the filter, written in Rust, as a binary in the toolbox
- The Preview CSS that uses the classes outputted by the filter
This will start transitioning the impl generator to be a more generic helper tool, with the impl generator as one of its component.
Also, drop the "-bin" from the name, because what else is it going to be?
