feat: add @theme/Markdown to allow user modify their own markdown react component

lib/theme/Docs/index.js

@@ -9,27 +9,10 @@ export default class Docs extends React.Component {
     const {route, docsData, siteConfig} = this.props;
     const currentDoc = docsData.find(data => data.path === route.path);
 
-    const highlight = Object.assign(
-      {},
-      {
-        version: '9.12.0',
-        theme: 'default'
-      },
-      siteConfig.highlight
-    );
-
-    // Use user-provided themeUrl if it exists, else construct one from version and theme.
-    const highlightThemeURL = highlight.themeUrl
-      ? highlight.themeUrl
-      : `https://cdnjs.cloudflare.com/ajax/libs/highlight.js/${
-          highlight.version
-        }/styles/${highlight.theme}.min.css`;
-
     return (
       <Layout {...this.props}>
         <Helmet>
           <title>{(currentDoc && currentDoc.title) || siteConfig.title}</title>
-          <link rel="stylesheet" type="text/css" href={highlightThemeURL} />
         </Helmet>
         <div className={styles.mainContainer}>{this.props.children}</div>
       </Layout>