fix: add missing styles and type stub for RichEditor

Author: wkylin

src/components/stateless/MdxEditor/MdxEditor.stories.jsx

@@ -0,0 +1,9 @@
+import React from 'react'
+import ProMdxEditor from './index'
+
+export default {
+  title: 'stateless/MdxEditor',
+  component: ProMdxEditor,
+}
+
+export const Default = () => <ProMdxEditor />

src/components/stateless/MdxEditor/styles/codeHighlight.less

@@ -0,0 +1,13 @@
+/* Minimal code highlight styles for MdxEditor */
+.mdx-code-block {
+  padding: 0.5rem;
+  border-radius: 6px;
+  background: #0b1220;
+  color: #e6eef8;
+}
+
+/* allow highlight.js / lowlight tokens to show */
+pre code .hljs {
+  background: transparent;
+  color: inherit;
+}

src/components/stateless/RichEditor/index.d.ts

@@ -0,0 +1,2 @@
+declare const RichEditor: any
+export default RichEditor