feat: add core domain model foundations

core/document.ts

@@ -0,0 +1,11 @@
+import type { Artboard } from "./artboard";
+import type { Asset } from "./asset";
+import type { DocumentId } from "./id";
+
+export type ImageDocument = {
+  id: DocumentId;
+  name: string;
+  version: number;
+  artboards: Artboard[];
+  assets: Asset[];
+};