Add process.thread.name (#36)

Author: felixbarny

spec/spec.json

@@ -76,6 +76,11 @@
                 "",
                 "The field helps to filter for different log streams from the same pod, for example and is required for log anomaly detection."
             ]
+        },
+        "process.thread.name": {
+            "type": "string",
+            "required": false,
+            "url": "https://www.elastic.co/guide/en/ecs/current/ecs-process.html"
         }
     }
 }