web-api-cat 0.7.17

Bindings between boa-cat (JS engine) and the DOM (html-cat tree) plus fetch (net-cat). v0.7.17 adds the `:empty` and `:root` structural pseudo-classes plus a semantic fix: `document.querySelector` / `querySelectorAll` / `getElementsByTagName` / `getElementsByClassName` now search the document root AND its descendants (matching browser spec), so `document.querySelector('html')` and `document.querySelector(':root')` both resolve correctly. Element APIs still walk descendants only. Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.