Update CHANGELOG.md for 8.18.0 (#285)

Author: andsel

CHANGELOG.md

@@ -3,6 +3,10 @@
   - Embeds Ingest Node components from Elasticsearch 9.0.0 prerelease
   - Compatible with Logstash 8.17+
 
+## 8.18.0
+  - Aligns with stack major and minor versions, no functional changes [#285](https://github.com/elastic/logstash-filter-elastic_integration/pull/285)
+  - Embeds Ingest Node components from Elasticsearch 8.18
+  
 ## 8.17.1
   - Provides a guidance in logs when plugin version mismatches with connected Elasticsearch `major.minor` version [#255](https://github.com/elastic/logstash-filter-elastic_integration/pull/255)
   - Embeds Ingest Node components from Elasticsearch 8.17