Document the Deployment Protection setting causing 401 Unauthorized f…

…or preview images in Vercel. fixes transitive-bullshit#435, fixes transitive-bullshit#437

readme.md

@@ -47,6 +47,7 @@ This project requires a recent version of Node.js (we recommend >= 16).
 3. `npm install`
 4. `npm run dev` to test locally
 5. `npm run deploy` to deploy to vercel 💪
+6. ❗Disable **Deployment Protection** setting in Vercel Web Dashboard ❗ ([See more below](#vercel-configuration))
 
 I tried to make configuration as easy as possible — All you really need to do to get started is edit `rootNotionPageId`.
 
@@ -58,6 +59,16 @@ In order to find your Notion workspace ID (optional), just load any of your site
 
 I recommend setting up a collection on your home page that contains all of your articles / projects / content. There are no structural constraints on your Notion workspace, however, so feel free to add content as you normally would in Notion.
 
+### Vercel Configuration
+#### Enabling social media preview images
+**❗❗❗Social media preview images won't work by default in Vercel❗❗❗**
+
+👉 You need Login to Vercel Dashboard and **disable Vercel Authentication** from `Project -> Settings -> Deployment Protection`.
+
+![Vercel Deployment Protection setting](https://github.com/transitive-bullshit/nextjs-notion-starter-kit/assets/5691777/9cce3b60-7102-4c34-a422-9f6572155c10 "Vercel Deployment Protection setting which causes social media preview image endpoint to return 401 Unauthorized")
+
+💡 If you forget to do this your site will return `401 Unauthorized` responses when crawlers are trying to retrieve the images
+
 ## URL Paths
 
 The app defaults to slightly different URL paths in dev vs prod (though pasting any dev pathname into prod will work and vice-versa).