<webview> Event object generation

[miniak]

• properties should not be optional
• it should directly extend the GlobalEvent

Example

interface UpdateTargetUrlEvent extends Event {
    url?: string;
}

should be

interface UpdateTargetUrlEvent extends GlobalEvent {
    url: string;
}

...

interface WebviewTag extends HTMLElement {
    ...
    addEventListener(event: 'did-finish-load', listener: (event: GlobalEvent) => void, useCapture?: boolean): this;
    removeEventListener(event: 'did-finish-load', listener: (event: GlobalEvent) => void): this;
    ...
    addEventListener(event: 'update-target-url', listener: (event: UpdateTargetUrlEvent) => void, useCapture?: boolean): this;
    removeEventListener(event: 'update-target-url', listener: (event: UpdateTargetUrlEvent) => void): this;
    ...
}

[MarshallOfSound]

The current interface here is

interface UpdateTargetUrlEvent extends Event {
  url: string;
}

Where Event directly extends GlobalEvent. I think we're all good here now and this just wasn't closed out