Update .meta/config.json files

We've recently introduced a change to the exercise's `.meta/config.json` format. See [the specification](https://github.com/exercism/v3/blob/master/docs/concept-exercises.md#metaconfigjson) 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](https://github.com/exercism/v3/pull/1184/files).