Runner metadata should expose keywords mappings

[flbulgarelli]

In order to truly support mumuki/mumuki-laboratory#1103, each runner should expose a dictionary compatible with mumuki/mumukit-inspection#14

The mappings should be indexed by locale, in order to also support different mappings when the language is internationalized:

{
   keywords: {
      en: {
          true: 'True'
      },
      es: {
         true: 'Verdadero'
      }
  }
}

[flbulgarelli]

We should also have separate keyword maps for custom editors and standard editors.

Alternatively, we could split gobstones and gobstones-jr runners, so that we can expose different mappings for each of them.