FlatGeoBuf as a Vector format

[A-Behairi]

I think it would make more sense for "FlatGeoBuf" to be configured as a type "Vector" source format instead of a type, as it is a data format that holds vector data. e.g:

{
        type: "Vector",
        properties: {
          id: "FlatGeoBufLayer",
          minZoom: 12,
        },
        source: {
          type: "Vector",
          url: "https://eox-gtif-public.s3.eu-central-1.amazonaws.com/admin_borders/STATISTIK_AUSTRIA_GEM_20220101.fgb",
          format: "FlatGeoBuf"
        },
}