Update WebDriver-BiDi user prompt algorithm

[Lightning00Blade]

Updates the prompt(message, default) algorithm to send the default as a third argument to to WebDriver BiDi user prompt opened. WebDriver-BiDi PR that is implementing this - w3c/webdriver-bidi#521.

• At least two implementers are interested (and none opposed):
  • …
  • …
• Tests are written and can be reviewed and commented upon at:
  • …
• Implementation bugs are filed:
  • Chromium: …
  • Gecko: …
  • WebKit: …
  • Deno (only for timers, structured clone, base64 utils, channel messaging, module resolution, web workers, and web storage): …
  • Node.js (only for timers, structured clone, base64 utils, channel messaging, and module resolution): …
• MDN issue is filed: …

(See WHATWG Working Mode: Changes for more details.)

---

/timers-and-user-prompts.html ( diff )

[domenic]

LGTM, will merge after the WebDriver BiDi change merges.