Clarify extension docs that custom extensions are not supported (supabase#38070)

* clarified extension support and linked to github discussion

* Update apps/docs/content/guides/database/extensions.mdx

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update apps/docs/content/guides/database/extensions.mdx

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* add dbdev reference

* add dbdev reference

* Update extensions.mdx

Co-authored-by: Chris Chinchilla <[email protected]>

* Update extensions.mdx

Co-authored-by: Chris Chinchilla <[email protected]>

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Chris Chinchilla <[email protected]>

Author: 3 people

apps/docs/content/guides/database/extensions.mdx

@@ -60,6 +60,10 @@ If a new version of an extension becomes available on Supabase, you need to init
 
 ### Full list of extensions
 
-Supabase is pre-configured with over 50 extensions. You can also install your own SQL extensions directly in the database through our SQL editor.
+Supabase is pre-configured with over 50 extensions and you can install additional extensions through the [database.dev](https://database.dev/) package manager.
+
+You can install pure SQL extensions directly in the database using the SQL editor or any Postgres client.
+
+If you would like to request an extension, add (or upvote) it in the [GitHub Discussion](https://github.com/orgs/supabase/discussions/33754).
 
 <Extensions />