[Feature Request]: Enhanced JSON output - fix/tweak on Append option

### What would you like to happen?

The Append option in the Enhanced JSON output transform actually works, but it appends multiple JSONs on the same line rather than creating a ND-JSON file (that contains a single valid JSON per line). An option to do that would be probably useful.

A workaround to create a ND-JSON file with Hop transforms only is the following:
- set the Enhanced JSON output transform to only output the value (not to write into a file)
- link the output to a Text File output component, and set the following options: enable "Append" and "Disable the enclosure fix", disable "Header". In the fields specify only the JSON string you get from the previous transform

### Issue Priority

Priority: 3

### Issue Component

Component: Transforms

Start with the Enhanced JSON output transform and inspect how its Append option writes multiple JSON values. Compare its behavior with the described Text File output workaround; the work is done when an append-enabled output produces ND-JSON with one valid JSON object per line.

Written by the indexing model from the issue text.