Kdl sketch

[clux]

does not work because kdl does not serialize with serde. for #56

error[E0277]: the trait bound `serde_json::Value: TryFrom<KdlDocument>` is not satisfied
   --> lq.rs:209:45
    |
209 |         let doc_as: serde_json::Value = doc.try_into()?;
    |                                             ^^^^^^^^ the trait `From<KdlDocument>` is not implemented for `serde_json::Value`, which is required by `KdlDocument: TryInto<_>`
    |