If you think it would be valuable to add such functionality to Meeseeks somehow (at the Elixir or Rust levels, maybe as a pre-parsing step, maybe as an option in parsing, maybe ???) and are willing to implement such functionality I suggest opening an issue so we can discuss how it might make sense to proceed.
Here was how from_bytes was implemented in html5ever: Add Parser::from_bytes, with BOM detection and Content-Type charset. · servo/html5ever@2f4f64b · GitHub
And here is the HTML5 spec for encoding sniffing: HTML Standard
