Merge pull request #169 from humanmade/backport-164-to-v5-branch

[Backport v5-branch] Add Sitemaps to v5 upgrade guide

other-docs/guides/upgrading/v5.md

@@ -37,6 +37,8 @@ If you use Local Chassis you will need to also update Chassis and its extensions
 
 ### SEO
 
+#### AMP & Facebook Instant Articles
+
 The AMP and Facebook Instant Articles plugins have been unbundled from Altis. This allows you to specify the versions of each directly in your Composer requirements. While these are no longer included with Altis, we plan to maintain compatibility with AMP in new features as necessary.
 
 If you're using AMP in your project, after updating your Altis requirements, you will need to additionally require the AMP plugin:
@@ -53,6 +55,14 @@ If you're using Facebook Instant Articles, you will need to require the FBIA plu
 $ composer require wpackagist-plugin/fb-instant-articles
 ```
 
+#### Sitemaps
+
+The MSM Sitemaps plugin previously used to provide the XML Sitemaps feature has been superseded by the new core support for Sitemaps introduced in WordPress 5.5. These core sitemaps were developed in collaboration between WordPress, Google and Human Made.
+
+The update may require you to re-submit your sitemap index file in [Google Search Console](https://search.google.com/search-console/) as it has been relocated from `/sitemap.xml` to `/wp-sitemap.xml`. The new index sitemap URL is automatically added to the `robots.txt` file.
+
+The filters provided by MSM Sitemaps that were previously documented are no longer available. Please [refer to updated Sitemaps documentation](docs://seo/xml-sitemaps.md) to learn how to achieve the same results.
+
 
 ## Headline Features