Add an attribute for ingest management (#1867)

* Add an attribute for ingest management

* Add ingest mgmt guide

* Shorten attribute name

shared/attributes.asciidoc

@@ -19,6 +19,7 @@
 :winlogbeat-ref:       https://www.elastic.co/guide/en/beats/winlogbeat/{branch}
 :heartbeat-ref:        https://www.elastic.co/guide/en/beats/heartbeat/{branch}
 :journalbeat-ref:      https://www.elastic.co/guide/en/beats/journalbeat/{branch}
+:ingest-guide:         https://www.elastic.co/guide/en/ingest-management/{branch}
 :apm-get-started-ref:  https://www.elastic.co/guide/en/apm/get-started/{branch}
 :apm-overview-ref-v:   https://www.elastic.co/guide/en/apm/get-started/{branch}
 :apm-overview-ref-70:  https://www.elastic.co/guide/en/apm/get-started/7.0
@@ -122,6 +123,7 @@ Ingest terms
 :agent: Elastic Agent
 :fleet: Fleet
 :ingest-manager: Ingest Manager
+:ingest-management: ingest management
 :package-manager: Elastic Package Manager
 :integrations: Integrations
 :package-registry: Elastic Package Registry