Exporting fields for content type
UPDATE

You might also try Drupal Console's drupal config:export:content:type command. 

It's description says:


  The config:export:content:type command Export a specific content type
  and their fields.




Content types and Fields are 2 separate configuration in Drupal 8, so if you want to export content type with fields you have to export all it's fields configurations too.

Features module might be helpful for grouping configurations, it's not stable yet, I haven't tried it but I think it might worth trying.