Adds 2.12 to version history (#6452) (#6469)

(cherry picked from commit 6803410)

Signed-off-by: Fanit Kolchina <[email protected]>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

_about/version-history.md

@@ -9,6 +9,7 @@ permalink: /version-history/
 
 OpenSearch version | Release highlights | Release date  
 :--- | :--- | :--- 
+[2.12.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.12.0.md) | Makes concurrent segment search and conversational search generally available. Provides an experimental OpenSearch Assistant Toolkit, including agents and tools, workflow automation, and OpenSearch Assistant for OpenSearch Dashboards UI. Adds a new match-only text field, query insights to monitor top N queries, and k-NN search on nested fields. For a full list of release highlights, see the Release Notes. | 20 February 2023
 [2.11.1](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.11.1.md) | Includes maintenance changes and bug fixes for cross-cluster replication, alerting, observability, OpenSearch Dashboards, index management, machine learning, security, and security analytics. For a full list of release highlights, see the Release Notes. | 30 November 2023
 [2.11.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.11.0.md) |  Adds multimodal and sparse neural search capability and the ability to take shallow snapshots that refer to data stored in remote-backed storage. Makes the search comparison tool generally available. Includes a simplified workflow to create threat detectors in Security Analytics and improved security in OpenSearch Dashboards. Experimental features include a new framework and toolset for distributed tracing and updates to conversational search. For a full list of release highlights, see the Release Notes. | 16 October 2023
 [2.10.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.10.0.md) |  Makes remote-backed storage generally available. Adds hybrid search capability, custom log types for Security Analytics, IP2Geo ingest processor, and delimited term frequency token filter. Includes a new look and feel for OpenSearch Dashboards and updates the Discover tool. Adds Microsoft Teams webhook support for notifications. Experimental features include concurrent segment search and conversational search. For a full list of release highlights, see the Release Notes. | 25 September 2023