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'

---------

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

document-legacy/src/document.rs

@@ -22,7 +22,7 @@ use std::hash::{Hash, Hasher};
 /// This does not technically need to be unique globally, only within a folder.
 pub type LayerId = u64;
 
-#[derive(Debug, Clone, Deserialize, Serialize)]
+#[derive(Debug, Clone, Deserialize, Serialize, specta::Type)]
 pub struct Document {
 	/// The root layer, usually a [FolderLayer](layers::folder_layer::FolderLayer) that contains all other [Layers](layers::layer_info::Layer).
 	pub root: Layer,