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>

document-legacy/src/layers/shape_layer.rs

@@ -16,7 +16,7 @@ use std::fmt::Write;
 /// elements inside a
 /// [`<g>`](https://developer.mozilla.org/en-US/docs/Web/SVG/Element/g)
 /// group that the transformation matrix is applied to.
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize, specta::Type)]
 pub struct ShapeLayer {
 	/// The geometry of the layer.
 	pub shape: Subpath,