Migrate code and documentation to wazuh-indexer-plugins repo (#678)

* Migrate code and documentation to wazuh-indexer-plugins repo

* Migrate operational--integrations_maintenance_request.md

* Remove ECS generator workflow

README.md

@@ -11,7 +11,6 @@
 [![GHA precommit](https://github.com/opensearch-project/OpenSearch/actions/workflows/precommit.yml/badge.svg)](https://github.com/opensearch-project/OpenSearch/actions/workflows/precommit.yml)
 [![Jenkins gradle check job](https://img.shields.io/jenkins/build?jobUrl=https%3A%2F%2Fbuild.ci.opensearch.org%2Fjob%2Fgradle-check%2F&label=Jenkins%20Gradle%20Check)](https://build.ci.opensearch.org/job/gradle-check/)
 [![Build packages](https://github.com/wazuh/wazuh-indexer/actions/workflows/build.yml/badge.svg)](https://github.com/wazuh/wazuh-indexer/actions/workflows/build.yml)
-[![ECS Generator](https://github.com/wazuh/wazuh-indexer/actions/workflows/generate-ecs-mappings.yml/badge.svg)](https://github.com/wazuh/wazuh-indexer/actions/workflows/generate-ecs-mappings.yml)
 
 
 - [Welcome!](#welcome)