feat(v2): Provide type definitions for MDXPage from page plugin (#3354)

packages/docusaurus-plugin-content-pages/src/plugin-content-pages.d.ts

@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+declare module '@theme/MDXPage' {
+  import type {MarkdownRightTableOfContents} from '@docusaurus/types';
+
+  export type Props = {
+    readonly content: {
+      readonly frontMatter: {
+        readonly title: string;
+        readonly description: string;
+      };
+      readonly metadata: {readonly permalink: string};
+      readonly rightToc: readonly MarkdownRightTableOfContents[];
+      (): JSX.Element;
+    };
+  };
+
+  const MDXPage: (props: Props) => JSX.Element;
+  export default MDXPage;
+}