Added retirement warning on Field customizers (#10308)

* Added retirement warning on Field customizers

I'm not sure on the wording, but there SHOULD be a warning on the page ensuring that people are aware of the upcoming retirement

* Update ms.date

* grammar fixes & msdocs alignment

* change note to warning

* fix build report finding

---------

Co-authored-by: Andrew Connell <[email protected]>

Author: Tanddant

docs/spfx/extensions/get-started/building-simple-field-customizer.md

@@ -1,15 +1,17 @@
 ---
 title: Build your first Field Customizer extension
 description: Extensions are client-side components that run inside the context of a SharePoint page. Extensions can be deployed to SharePoint Online, and you can use modern JavaScript tools and libraries to build them.
-ms.date: 12/14/2023
+ms.date: 06/18/2025
 ms.custom: scenarios:getting-started
 ---
-
 # Build your first Field Customizer extension
 
+> [!WARNING]
+> Microsoft [announced field customizers are deprecated](https://support.microsoft.com/en-gb/office/support-update-for-sharepoint-framework-field-customizers-in-lists-and-document-libraries-0eccc64e-4512-47df-9da0-d855be22fb0a#) on June 13, 2025, and will be retired on June 30, 2026. Consider [ListView Command Set extensions](./building-simple-cmdset-with-dialog-api.md) or [use column formatting to customize SharePoint](../../../declarative-customization/column-formatting.md) instead of field customizers.
+
 Extensions are client-side components that run inside the context of a SharePoint page. Extensions can be deployed to SharePoint Online, and you can use modern JavaScript tools and libraries to build them.
 
-You can follow these steps by watching the video on the Microsoft 365 Platform Communtiy (PnP) YouTube Channel:
+You can follow these steps by watching the video on the Microsoft 365 Platform Community (PnP) YouTube Channel:
 
 > [!Video https://www.youtube.com/embed/mBZ7Sq_KfDA]