This is HTML to JSON, written in Rust, and there's also pup[1] which I found out about just the other day on HN[2] which uses a very similar syntax (CSS selectors) but outputs HTML and is written in Go.
I can see room for both though it would interesting to have a more detailed comparison to go on (e.g. types of HTML, speed etc).
[1] https://github.com/ericchiang/pup
[2] https://news.ycombinator.com/item?id=33805732