docs(developers): federated docs

DEVELOPERS.md

@@ -132,6 +132,26 @@ Create a new entry in the [`redirects.js`](https://github.com/supabase/supabase/
 
 ---
 
+### Federated docs
+
+We support "federating" docs, meaning doc content can come directly from external repos other than [`supabase/supabase`](https://github.com/supabase/supabase).
+
+- It's great for things like client libs who have their own set of docs that we don't want to duplicate on the official Supabase docs (eg. [`supabase/vecs`](https://github.com/supabase/vecs)).
+- No duplication or manual steps required - fetches and generates automatically as part of the docs build pipeline
+- It's flexible - you can "embed" external docs nearly anywhere at any level in Supabase docs, but they will feel native
+- If you are maintaining a repo containing docs that you think could also live in Supabase docs, feel free to create an issue and we can work together to integrate
+
+Federated docs work using Next.js's build pipeline. We use `getStaticProps()` to fetch remote documentation (ie. markdown) at build time which is processed and passed to the respective page within the docs.
+
+See the [Vecs Python source code](https://github.com/supabase/supabase/blob/master/apps/docs/pages/guides/ai/python/%5Bslug%5D.tsx) to see how we do this for [`supabase/vecs`](https://github.com/supabase/vecs). Use this as a starting point for federating other docs.
+
+Some things to consider:
+
+- Links will often need to be transformed. For example if you are bringing in external markdown content, they may contain relative links that may not translate 1-to-1 after rendering in the Supabase docs. Use the [Link Transform](https://github.com/supabase/supabase/blob/master/apps/docs/lib/mdx/plugins/rehypeLinkTransform.ts) rehype plugin to transform links.
+- External markdown may contain syntax extensions that Supabase docs don't understand by default (eg. [mkdocs-material extensions](https://squidfunk.github.io/mkdocs-material/setup/extensions/python-markdown)). We've built a few remark plugins to support these extensions (eg. [MkDocs Admonition](https://github.com/supabase/supabase/blob/master/apps/docs/lib/mdx/plugins/remarkAdmonition.ts)). If there is a markdown extension that you need that isn't built yet, feel free to open an issue and we can work together to create it.
+
+---
+
 ## Community channels
 
 If you are stuck somewhere or have any questions, join our [Discord Community Server](https://discord.supabase.com/) or the [Github Discussions](https://github.com/supabase/supabase/discussions). We are here to help!