Remove "game name" redundancies in config.json

[TadCordle]

Game names are defined in games, but then categories and levels are indexed by the same game names. Maybe it should all just be nested.

Idea: instead of

{
  "games": { "game name": [ ... ]" },
  "categories": { "game name": { ... } },
  "levels": {"game name": { ... } }
}

it should be

{
  "games": {
    "game name": {
      "aliases": [ ... ]
      "categories": { ... },
      "levels": { ... }
    }
  }
}