various cleanup

Author: marciw

docs/reference/breaking-changes-policy.md

@@ -33,3 +33,6 @@ Major releases (e.g. 7.x → 8.x) can include larger refactorings of the API spe
 
 All Elasticsearch APIs have stability indicators, which imply potential changes. If an API is `stable` only additional non-breaking changes are added. In case of `experimental` APIs, breaking changes can be introduced any time, which means that these changes, will also be reflected in the Java API Client.
 
+## Breaking changes by release
+
+For more information, refer to the [](../release-notes/index.md).

docs/reference/release-highlights.md

@@ -9,6 +9,6 @@ These are the important new features and changes in minor releases. Every releas
 
 For a list of detailed changes, including bug fixes, please see the [GitHub project realease notes](https://github.com/elastic/elasticsearch-java/releases).
 
-### 9.0.0 [release-highlights-900]
+## 9.0.0 [release-highlights-900]
 
-[Release Notes](/release-notes/9-0-0.md)
+[Release notes](/release-notes/9-0-0.md)

docs/release-notes/9-0-0.md

@@ -3,9 +3,9 @@ navigation_title: "9.0.0"
 ---
 # Elasticsearch Java Client 9.0.0 [elasticsearch-java-client-900]
 
-Discover what changed in the 9.0.0 version of the java client. 
+Discover what changed in the 9.0.0 version of the Java client. 
 
-### Breaking Changes [elasticsearch-java-client-900-breaking-changes]
+### Breaking changes [elasticsearch-java-client-900-breaking-changes]
 
 ::::{dropdown} Server accurate aggregation number values  
 In previous versions of the client, when the server returned number that was both always present and could be `null` (for example Aggregation results), the client would default to `0` and deserialize the number into a primitive data type instead of an Object. This design choice was changed in this version, changing the fields type to support `null` and be coherent with the server response.

docs/release-notes/index.md

@@ -9,3 +9,6 @@ mapped_pages:
 Review the changes, fixes, and more in each version of Elasticsearch Java Client.
 
 To check for security updates, go to [Security announcements for the Elastic stack](https://discuss.elastic.co/c/announcements/security-announcements/31).
+
+## 9.0.0
+[Release notes](../release-notes/9-0-0.md)