Clarify og:image behavior in SEO documentation (#1464)

* Update optimize/seo.mdx

* move note

---------

Co-authored-by: mintlify[bot] <109931778+mintlify[bot]@users.noreply.github.com>
Co-authored-by: Ethan Palm <[email protected]>

Author: mintlify[bot]

optimize/seo.mdx

@@ -42,6 +42,10 @@ title: "Your example page title"
 ## Common meta tags reference
 Below is a comprehensive list of meta tags you can add to your `docs.json`. These meta tags help improve your site's SEO, social sharing, and browser compatibility.
 
+<Note>
+  The `og:image` adds a background image that Mintlify automatically overlays with your logo, page title, and description when generating social media previews.
+</Note>
+
 You can preview how your meta tags will appear on different platforms using [metatags.io](https://metatags.io/).
 
 ```json expandable