Add support for select from arrays within a JSON object

It would be nice to have the possibility to select from arrays within a JSON object (as mentioned in https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-glacier-select-sql-reference-select.html).

Corresponding aws `SELECT` command would be something like
```
SELECT price FROM S3Object[*].books[*].price
```

A new option `-a/--array` could be added to do so.

I can submit a PR if needed.