Update .meta/config.json files

[ErikSchierboom]

We've recently introduced a change to the exercise's .meta/config.json format. See the specification for the new format. Please update your exercises's to the new format.

Concretely, this will mean putting moving the author(s) (the people that did the initial PR to add the exercise to your track) should be moved from the contributors key to the authors key. Furthermore, if you've used another exercise as the base of your exercise (i.e. it is a fork), please specifying forked exercise in the forked_from array.

For an example on what a PR can look like to update these files, see this F# PR.

[ErikSchierboom]

CC @exercism/dart