Add 2.8 to version history (#4241)

Signed-off-by: Fanit Kolchina <[email protected]>

version-history.md

@@ -10,6 +10,7 @@ permalink: /version-history/
 
 OpenSearch version | Release highlights | Release date  
 :--- | :--- | :--- 
+[2.8.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.8.0.md) | Adds cross-cluster query with PPL, search pipelines, an option to turn on segment replication as the default replication type, improved searchable snapshot performance, and Amazon OpenSearch Serverless support with SigV4 authentication for multiple data sources. Includes the UI for the flush, refresh, and clear cache operations in OpenSearch Dashboards. For a full list of release highlights, see the Release Notes. | 06 Jun 2023
 [2.7.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.7.0.md) | Includes searchable snapshots and segment replication, which are now generally available. Adds multiple data sources, observability features, dynamic tenant management, component templates, and shape-based map filters in OpenSearch Dashboards. Includes the flat object field type, hot shard identification, and a new automatic reloading mechanism for ML models. For a full list of release highlights, see the Release Notes. | 02 May 2023
 [2.6.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.6.0.md) | Includes simple schema for observability, index management UI enhancements, Security Analytics enhancements, search backpressure at the coordinator node level, and the ability to add maps to dashboards. Experimental features include a new ML model health dashboard, new text embedding models in ML, and SigV4 authentication in Dashboards. For a full list of release highlights, see the Release Notes. | 28 February 2023
 [2.5.0](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-2.5.0.md) | Includes index management UI enhancements, multi-layer maps, Jaeger support for observability, Debian distributions, returning cluster health by awareness attribute, cluster manager task throttling, weighted zonal search request routing policy, and query string support in index rollups. Experimental features include request-level durability in remote-backed storage and GPU acceleration for ML nodes. For a full list of release highlights, see the Release Notes. | 24 January 2023