Add license

Author: eric-forte-elastic

detection_rules/esql_errors.py

@@ -1,3 +1,8 @@
+# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+# or more contributor license agreements. Licensed under the Elastic License
+# 2.0; you may not use this file except in compliance with the Elastic License
+# 2.0.
+
 """ESQL exceptions."""
 
 from elasticsearch import Elasticsearch  # type: ignore[reportMissingTypeStubs]