Create phantom for WIP ingest-processor (#3306)

Author: shainaraskas

config/navigation.yml

@@ -12,6 +12,7 @@ phantoms:
   - toc: docs-content://release-notes/apm-agents
   - toc: docs-content://
   - toc: cloud://release-notes
+  - toc: elasticsearch://reference/ingest-processor
 
 toc:
   #############