Add `statistics.country_rank` to `/users` API batch return response

[Calemy]

I'm surprised that i'm not receiving the country rank on this endpoint since i think that it is a keypart of a user's profile just like the global rank.

This is the response i get back from "response.statistics_rulesets":

{
  level: { current: 54, progress: 8 },
  global_rank: 35128,
  global_rank_exp: null,
  pp: 3389.1,
  pp_exp: 0,
  ranked_score: 150177815,
  hit_accuracy: 95.1472,
  play_count: 4856,
  play_time: 319838,
  total_score: 1040177952,
  total_hits: 3386128,
  maximum_combo: 2558,
  replays_watched_by_others: 0,
  is_ranked: true,
  grade_counts: { ss: 0, ssh: 2, s: 47, sh: 1, a: 67 }
}