Groundwork for integrating Specta (#949)

* add derive(specta::Type)

* use specta from git

* introduce Uuid type

* remove unnecessary specta::Type

* document export_types test

* upgrade Specta
The previous Specta branch had some hacks that were just for this project. They have all been converted into proper features so they can be merged into main.

* remove some unnecessary specta::Type uses

* add MessageDiscriminantDef explanation

* manually export types with specta

* rename 'specta.rs' to 'export_types.rs'

* rename 'export_types' to 'generate_ts_types'

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Co-authored-by: Oscar Beaumont <oscar@otbeaumont.me>

editor/Cargo.toml

@@ -31,6 +31,7 @@ kurbo = { git = "https://github.com/linebender/kurbo.git", features = [
 remain = "0.2.2"
 derivative = "2.2.0"
 once_cell = "1.13.0" # Remove when `core::cell::OnceCell` is stabilized (<https://doc.rust-lang.org/core/cell/struct.OnceCell.html>)
+specta.workspace = true
 
 # Node graph
 image = { version = "0.24", default-features = false, features = ["bmp"] }