feat: add code samples for Actor object

[m-murasovs]

More code samples for the API docs. Please merge after approving 🙏

[netmilk]

I feel like we should approach the substitutions the same way the other generated examples do that.

The users won't read the comment line and the parseable example won't throw an exception, but it will result in non-2xx. A placeholder e.g. <ACTOR ID> would throw. Another approach might be using overly obvious placeholders e.g. johndoe/foo-bar-actor.

Also, please try to prevent horizontal scrolling wherever possible.
e.g.

const { items } = await apifyClient
  .actors()
  .list();