feat: Expose undo/redo actions to host app

Enable navigating editor history from the host app.

ios/Sources/GutenbergKit/Sources/EditorViewController.swift

@@ -207,6 +207,16 @@ public final class EditorViewController: UIViewController, GutenbergEditorContro
         return EditorTitleAndContent(title: title, content: content)
     }
 
+    /// Steps backwards in the editor history state
+    public func undo() {
+        evaluate("editor.undo();")
+    }
+
+    /// Steps forwards in the editor history state
+    public func redo() {
+        evaluate("editor.redo();")
+    }
+
     /// Enables code editor.
     public var isCodeEditorEnabled: Bool = false {
         didSet {

src/components/visual-editor/index.jsx

@@ -72,7 +72,7 @@ function VisualEditor({ post }) {
 	const postContentRef = useRef(post.content);
 	const { addEntities, editEntityRecord, receiveEntityRecords } =
 		useDispatch(coreStore);
-	const { setEditedPost, setupEditor } = useDispatch(editorStore);
+	const { setEditedPost, setupEditor, undo, redo } = useDispatch(editorStore);
 	const { getEditedPostAttribute, getEditedPostContent } =
 		useSelect(editorStore);
 
@@ -171,6 +171,16 @@ function VisualEditor({ post }) {
 		};
 	};
 
+	editor.undo = () => {
+		// Do not return the `Promise` return value to avoid host errors.
+		undo();
+	};
+
+	editor.redo = () => {
+		// Do not return the `Promise` return value to avoid host errors.
+		redo();
+	};
+
 	const blockEditorSettings = useBlockEditorSettings(
 		editorSettings,
 		post.type,