Add mdx components for guide

components/mdx-components/index.js

@@ -1,3 +1,13 @@
-const MdxComponents = {};
+import P from './p';
+import { Headings } from './heading';
+import { Pre } from './pre';
+import { BlockQuote } from './blockquote';
+
+const MdxComponents = {
+  p: P,
+  ...Headings,
+  pre: Pre,
+  blockquote: BlockQuote,
+};
 
 export default MdxComponents;