Add `CommandEvent` to the web-sys

[mskorkowski]

Adds the CommandEvent from the Invoker Commands API.

• CommandEvent spec - https://html.spec.whatwg.org/#the-commandevent-interface
• MDN page about Invoker commands API - https://developer.mozilla.org/en-US/docs/Web/API/Invoker_Commands_API

MDN page indicates that most of desktop browsers do support the CommandEvent.

PR #4552 is ready for review