Release note for GA of extended attrs (#4601)

## What are you changing in this pull request and why?

Create release note to announce GA of extended attributes feature in dbt
Cloud.

## Checklist

- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
so my content adheres to these guidelines.
- [x] For [docs
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#about-versioning),
review how to [version a whole
page](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
and [version a block of
content](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#versioning-blocks-of-content).
- [ ] Needs review from PM

Adding new pages (delete if not applicable):
- ~~[ ] Add page to `website/sidebars.js`~~ N/A -- automated for release
notes
- [x] Provide a unique filename for the new page

website/docs/docs/dbt-versions/release-notes/74-Dec-2023/external-attributes.md

@@ -0,0 +1,16 @@
+---
+title: "Update: Extended attributes is GA"
+description: "December 2023: The extended attributes feature is now GA in dbt Cloud. It enables you to override dbt adapter YAML attributes at the environment level."
+sidebar_label: "Update: Extended attributes is GA"
+sidebar_position: 10
+tags: [Dec-2023]
+date: 2023-12-06
+---
+
+The extended attributes feature in dbt Cloud is now GA! It allows for an environment level override on any YAML attribute that a dbt adapter accepts in its `profiles.yml`. You can provide a YAML snippet to add or replace any [profile](/docs/core/connect-data-platform/profiles.yml) value.
+
+To learn more, refer to [Extended attributes](/docs/dbt-cloud-environments#extended-attributes).
+
+The **Extended Atrributes** text box is available from your environment's settings page: 
+
+<Lightbox src="/img/docs/dbt-cloud/using-dbt-cloud/extended-attributes.jpg" width="85%" title="Example of the Extended Attributes text box" />