Update mdx-bundler links

Author: pomber

examples/mdx-bundler/README.md

@@ -0,0 +1,3 @@
+# mdx-bundler + Code Hike
+
+See [this guide](https://codehike.org/docs/installation/mdx-bundler) or try it on [Stackblitz](https://stackblitz.com/github/code-hike/codehike/tree/main/examples/mdx-bundler).

examples/mdx-bundler/src/posts.js

@@ -4,11 +4,9 @@ import { remarkCodeHike } from "@code-hike/mdx"
 import theme from "shiki/themes/material-palenight.json"
 import { bundleMDX } from "mdx-bundler"
 
-const POSTS_PATH = path.join(process.cwd(), "posts")
-
 export function getPostNames() {
   return fs
-    .readdirSync(POSTS_PATH)
+    .readdirSync("posts")
     .filter((path) => /\.mdx?$/.test(path))
     .map((fileName) => {
       const postName = fileName.replace(/\.mdx?$/, "")