[docs][ingest-processors] Updated Example in Docs of append processor (…

…elastic#36478)

* Updated Example in Docs of append processor

* Reworded the sentence in documentation

libbeat/processors/actions/docs/append.asciidoc

@@ -8,10 +8,10 @@
 The `append` processor appends one or more values to an existing array if the target field already exists and it is an array. Converts a scaler to an array and appends one or more values to it if the field exists and it is a scaler. Here the values can either be one or more static values or one or more values from the fields listed under 'fields' key.
 
 `target_field`:: The field in which you want to append the data.
-`fields`:: (Optional) List of fields from which you want to copy data from. If the value is of a concrete type it will be appended directly to the target. 
+`fields`:: (Optional) List of fields from which you want to copy data from. If the value is of a concrete type it will be appended directly to the target.
 However, if the value is an array, all the elements of the array are pushed individually to the target field.
 `values`:: (Optional) List of static values you want to append to target field.
-`ignore_empty_values`:: (Optional) If set to `true`, all the `""` and `nil` are omitted from being appended to the target field.  
+`ignore_empty_values`:: (Optional) If set to `true`, all the `""` and `nil` are omitted from being appended to the target field.
 `fail_on_error`:: (Optional) If set to `true` and an error occurs, the changes are reverted and the original is returned. If set to `false`,
 processing continues if an error occurs. Default is `true`.
 `allow_duplicate`:: (Optional) If set to `false`, the processor does not append values already present in the field. The default is `true`, which will append duplicate values in the array.
@@ -30,26 +30,34 @@ processors:
       fields: message
       target: ""
   - append:
-      target_field: my-target-field
-      fields: 
+      target_field: target-field
+      fields:
         - concrete.field
         - array.one
-      values: 
+      values:
         - static-value
         - ""
       ignore_missing: true
       fail_on_error: true
       ignore_empty_values: true
 ------------------------------------------------------------------------------
 
-Copies the values of `concrete.field`, `array.one` from response field to `my-target-field`:
+Copies the values of `concrete.field`, `array.one` response fields and the static values to `target-field`:
 
 [source,json]
 -------------------------------------------------------------------------------
 {
-  "message": "my-interesting-message",
-  "event": {
-      "original": "my-interesting-message"
-  }
+  "concrete": {
+    "field": "val0"
+  },
+  "array": {
+      "one": [ "val1", "val2" ]
+  },
+  "target-field": [
+    "val0",
+    "val1",
+    "val2",
+    "static-value"
+  ]
 }
 -------------------------------------------------------------------------------