Support unrolling arrays

[feliwir]

Hey, I got a struct like this (small sample):

#[derive(Default, Debug, PartialEq, Deserialize)]
#[serde(default, deny_unknown_fields, rename_all = "PascalCase")]
pub struct GlobalData {
    pub vertex_water_available_maps: [String; 4],
}

Which is serialized like this:

GameData
  VertexWaterAvailableMaps1 = "sample"
  VertexWaterAvailableMaps2 = "sample"
  VertexWaterAvailableMaps3 = "sample"
  VertexWaterAvailableMaps4 = "sample"
End

I'd love support a field attribute #[serde(unroll)].
Optional:

• Specify the start index (e.g. 0/1 or 'A'/'B')
• Specify the suffix type (numerical or alpha)

I know this is not a trivial feature, but I got literally hundreds of arrays like these. Unrolling them manually makes them less accessible and code a lot harder to read.

The complete format I'm currently deserializing can be seen here