feature request: `limit-access-to-actors`

I'd like to limit not by actor, but by a set of actors. Superficially it seems like it's possible;

```js
const keys = await octokit.users.listPublicKeysForUser({
  username: actor
})
```

assuming this will work with any actor, not just the one that initiated the action? 

If you're up for it, I can send a PR.