[Docs] Add Journalbeat and Functionbeat to stack getting started (#162)

Author: dedemorton

docs/en/getting-started/get-started-stack.asciidoc

@@ -323,7 +323,9 @@ Started documentation:
 |Elastic {beats} | To capture
 |{auditbeat-ref}/auditbeat-getting-started.html[{auditbeat}] |Audit data
 |{filebeat-ref}/filebeat-getting-started.html[{filebeat}] |Log files
+|{functionbeat-ref}/functionbeat-getting-started.html[{functionbeat}] |Cloud data
 |{heartbeat-ref}/heartbeat-getting-started.html[{heartbeat}] |Availability monitoring
+|{journalbeat-ref}/journalbeat-getting-started.html[{journalbeat}] |Systemd journals
 |{metricbeat-ref}/metricbeat-getting-started.html[{metricbeat}] |Metrics
 |{packetbeat-ref}/packetbeat-getting-started.html[{packetbeat}] |Network traffic
 |{winlogbeat-ref}/winlogbeat-getting-started.html[{winlogbeat}] |Windows event logs