docs: add metadata storage hooks docs

README.md

@@ -188,6 +188,86 @@ export default function Page() {
 ```
 </details>
 
+### Asset metadata storage hooks (callbacks)
+
+By default the asset metadata is stored in a JSON file in the `/videos` directory. 
+If you want to store the metadata in a database or elsewhere you can customize
+the storage hooks in a separate next-video config file.
+
+The below example config shows the default storage hooks for the JSON file storage.
+
+These hooks can be customized to fit your needs by changing the body of the
+`loadAsset`, `saveAsset`, and `updateAsset` functions.
+
+```js
+// next-video.mjs
+import { NextVideo } from 'next-video/process';
+import path from 'node:path';
+import { mkdir, readFile, writeFile } from 'node:fs/promises';
+
+export const { GET, POST, handler, withNextVideo } = NextVideo({
+  // Other next-video config options should be added here if using a next-video config file. 
+  // folder: 'videos',
+  // path: '/api/video',
+
+  loadAsset: async function (assetPath) {
+    const file = await readFile(assetPath);
+    const asset = JSON.parse(file.toString());
+    return asset;
+  },
+  saveAsset: async function (assetPath, asset) {
+    try {
+      await mkdir(path.dirname(assetPath), { recursive: true });
+      await writeFile(assetPath, JSON.stringify(asset), {
+        flag: 'wx',
+      });
+    } catch (err) {
+      if (err.code === 'EEXIST') {
+        // The file already exists, and that's ok in this case. Ignore the error.
+        return;
+      }
+      throw err;
+    }
+  },
+  updateAsset: async function (assetPath, asset) {
+    await writeFile(assetPath, JSON.stringify(asset));
+  }
+});
+```
+
+Then import the `withNextVideo` function in your `next.config.mjs` file.
+
+```js
+// next.config.mjs
+import { withNextVideo } from './next-video.mjs';
+
+/** @type {import('next').NextConfig} */
+const nextConfig = {};
+
+export default withNextVideo(nextConfig);
+```
+
+Lastly import the `GET` and `POST`, or `handler` functions in your API routes as you see fit.
+The handlers expect a `url` query or body parameter with the video source URL.
+
+These are the most minimal examples for the handlers, typically you would add
+more error handling and validation, authentication and authorization.
+
+**App router (Next.js >=13)**
+
+```js
+// app/api/video/route.js
+export { GET, POST } from '@/next-video';
+```
+
+**Pages router (Next.js)**
+
+```js
+// pages/api/video/[[...handler]].js
+export { handler as default } from '@/next-video';
+```
+
+
 ### Player only ([Demo](https://next-video-demo.vercel.app/player-only))
 
 Since [`v1.1.0`](https://github.com/muxinc/next-video/releases/tag/v1.1.0) you can import the player component directly and use it without any upload and processing features.