Add etcdbeat to the community beats (#4915)

libbeat/docs/communitybeats.asciidoc

@@ -32,6 +32,7 @@ https://github.com/Pravoru/consulbeat[consulbeat]:: Reads services health checks
 https://github.com/Ingensi/dockbeat[dockbeat]:: Reads Docker container
 statistics and indexes them in Elasticsearch.
 https://github.com/radoondas/elasticbeat[elasticbeat]:: Reads status from an Elasticsearch cluster and indexes them in Elasticsearch.
+https://github.com/gamegos/etcdbeat[etcdbeat]:: Reads stats from the Etcd v2 API and indexes them into Elasticsearch.
 https://github.com/christiangalsterer/execbeat[execbeat]:: Periodically executes shell commands and sends the standard output and standard error to
 Logstash or Elasticsearch.
 https://github.com/jarpy/factbeat[factbeat]:: Collects facts from https://puppetlabs.com/facter[Facter].