message: add current_user_playling_track()
diff: @@ -719,7 +719,21 @@ impl Spotify {
  let result = self.get(&mut url, &mut dumb);
  self.convert_result::<PrivateUser>(&result.unwrap_or_default())
  }
  + ///Get detailed profile information about the current user.
  + ///An alias for the 'me' method.
  + pub fn current_user(&self) -> Result<PrivateUser> {
  + self.me()
  + }
  + /// https://developer.spotify.com/web-api/get-the-users-currently-playing-track/
  + /// Get information about the current users currently playing track.
  + pub fn current_user_playing_track(&self, market: impl Into<Option<String>>) {
  + let market = market.into().unwrap_or("US".to_owned());
  + let mut params = HashMap::new();
  + params.insert("market", market);
  + let mut url = String::from("me/player/currently-playing");
  + self.get(&mut url, &mut params);
  + }
  fn convert_result<'a, T: Deserialize<'a>>(&self, input: &'a str) -> Result<T> {
  