Put the description in correct order plus little extension to the description

Author: andsel

CHANGELOG.md

@@ -1,3 +1,6 @@
+## x.y.z
+ - [DOC] described `executor_threads` configuration parameter [#421](https://github.com/logstash-plugins/logstash-input-beats/pull/421)
+
 ## 6.1.3
  - Fix: safe-guard byte buf allocation [#420](https://github.com/logstash-plugins/logstash-input-beats/pull/420) 
  - Updated Jackson dependencies

docs/index.asciidoc

@@ -122,8 +122,8 @@ This plugin supports the following configuration options plus the <<plugins-{typ
 | <<plugins-{type}s-{plugin}-add_hostname>> |<<boolean,boolean>>|No
 | <<plugins-{type}s-{plugin}-cipher_suites>> |<<array,array>>|No
 | <<plugins-{type}s-{plugin}-client_inactivity_timeout>> |<<number,number>>|No
-| <<plugins-{type}s-{plugin}-executor_threads>> |<<number,number>>|No
 | <<plugins-{type}s-{plugin}-ecs_compatibility>> | <<string,string>>|No
+| <<plugins-{type}s-{plugin}-executor_threads>> |<<number,number>>|No
 | <<plugins-{type}s-{plugin}-host>> |<<string,string>>|No
 | <<plugins-{type}s-{plugin}-include_codec_tag>> |<<boolean,boolean>>|No
 | <<plugins-{type}s-{plugin}-port>> |<<number,number>>|Yes
@@ -171,14 +171,6 @@ The list of ciphers suite to use, listed by priorities.
 
 Close Idle clients after X seconds of inactivity.
 
-[id="plugins-{type}s-{plugin}-executor_threads"]
-===== `executor_threads`
-
-  * Value type is <<number,number>>
-  * Default value is 1 executor thread per CPU core
-
-The number of parallel executor threads.
-
 [id="plugins-{type}s-{plugin}-ecs_compatibility"]
 ===== `ecs_compatibility`
 
@@ -192,6 +184,14 @@ The number of parallel executor threads.
 
 Refer to <<plugins-{type}s-{plugin}-ecs_metadata,ECS mapping>> for detailed information.
 
+[id="plugins-{type}s-{plugin}-executor_threads"]
+===== `executor_threads`
+
+  * Value type is <<number,number>>
+  * Default value is 1 executor thread per CPU core
+
+The number of parallel executor threads to be used to process incoming beats requests.
+
 [id="plugins-{type}s-{plugin}-host"]
 ===== `host`