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>

editor/src/messages/message.rs

@@ -62,3 +62,10 @@ impl Message {
 		s.finish()
 	}
 }
+
+/// Provides an impl of `specta::Type` for `MessageDiscriminant`, the struct created by `impl_message`.
+/// Specta isn't integrated with `impl_message`, so a remote impl must be provided using this
+/// struct.
+#[derive(specta::Type)]
+#[specta(inline, remote = "MessageDiscriminant")]
+pub struct MessageDiscriminantDef(u8);