existing-client-event and POST navigations

[alancutter]

If the user performs a POST method navigation into the scope of a web app who has "capture_links": "existing-client-event" should the POST data be retained in the launch event?

We should probably expose a Request object rather than just the URL that got captured.

Possible launch event API:

interface LaunchParams {
  readonly attribute Request capturedNavigation;
  readonly attribute FrozenArray<FileSystemHandle> files;
}

How would the site invoke this POST navigation? I think at the moment the web only has form elements to be able to do POST navigations for the document. Location.assign() should probably be updated to accept Request objects.