lint(track_config): check for concept-prerequisite cycles (#425)
lint(track_config): check for concept-prerequisite cycles (#425)

With this commit, `configlet lint` now checks that Concept Exercises in
a track-level `config.json` file satisfy the below rule:

- There must not be any cycles between `exercises.concept[].concepts`
  and `exercises.concept[].prerequisites`

Co-authored-by: ee7 <6cd0bf6d6fb42eedb0ac66182c815fd97fb4f715@users.noreply.github.com>

exercism/configlet