hackernews: fetch child comments

- Currently I only fetch the direct replies to a thread, not replies to the replies.
- Rationale is:
  1) It will increase the display response time (on raw output)
  2) Some comments tend to go too depth which might make it unusable
- A solution might be on raw mode at least, fetch but only a couple of levels deep.
- On TUI, this might be addresses with dynamic requests.