`RcDom` issues in `html2html` example

I am trying to figure out how to use this parser, and as far as I can tell, the only "getting started" documentation you provide is the html2html example.

html2html uses the markup5ever_rcdom package, which you have decided to make "unofficial" because it is unsafe and incorrect. This means two things:

1. The html2html example doesn't build by default and provides the message "the trait TreeSink is not implemented for RcDom". It took me quite a lot of hair pulling to figure out that you must pin the markup5ever_rcdom to version 0.5.0-unofficial to fix that problem.

2. If the only documentation you have for using this crate is a bad implementation, how am I supposed to use it? If you had some documentation on how I could write my own RcDom that would go a long way, but I don't see any.

Start with the html2html example and reproduce its default build failure, then inspect how it depends on markup5ever_rcdom. Review the linked discussion about RcDom's unofficial status and determine what documentation is needed for writing a custom RcDom. Done means the example's dependency guidance is correct and users have usable documentation for parser integration.