web-api-cat 0.6.0

Bindings between boa-cat (JS engine) and the DOM (html-cat tree) plus fetch (net-cat). v0.6.0 bumps to boa-cat 0.7 + ecma-parse-cat 0.3 so the v0.4 `document.cookie` accessor pair and the v0.5 `Value::Promise(_)` arms compose with user-supplied scripts using natural async syntax (`async () => body`, `async function foo() { ... }`, and reserved-word member access like `obj.catch(cb)`). No source change. Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.