jsonp: add jsonp command allowing non-nested JSON to CSV conversion with Polars

[rzmk]

#1878 covers the example and use case for this new command qsv jsonp.

Excerpt from qsv jsonp --help

Convert non-nested JSON to CSV (polars feature only). You may provide JSON data either from stdin or a file path. This command may not work with nested JSON data.

As a basic example, say we have a file fruits.json with contents:

[
    {
        "fruit": "apple",
        "price": 2.5
    },
    {
        "fruit": "banana",
        "price": 3.0
    }
]

To convert it to CSV format, run:

qsv jsonp fruits.json

And the following is printed to the terminal:

fruit,price
apple,2.5
banana,3.0

If fruits.json was provided using stdin then either use - or do not provide a file path. For example:

cat fruits.json | qsv jsonp -

Sample usage

Create a CSV file fruits.csv based on fruits.json:

cat fruits.json | qsv jsonp -o fruits.csv

Print to terminal the converted CSV data from a JSON file you may pick from a file dialog which is filtered to show .json files only:

qsv prompt -F json | qsv jsonp

Potential improvements

• This command relies on the polars feature being enabled, so an implementation without the feature being enabled and converting this command from jsonp to json is a potential improvement.
• Allowing nested JSON file conversion (may be customizable with options).

[jqnatividad]

Thanks for this new command @rzmk!
With this, we now have increased JSON compatibility beyond the less common JSONL format.