Jsonlines append mode
**Description**: Adding support to append mode for `to_json` when 'orient' is `records` and 'lines' is `True`

**Motivation**: [jsonlines](http://jsonlines.org/) is a format that is gaining some space (e.g. [Cloud Storage](https://cloud.google.com/bigquery/docs/loading-data-cloud-storage-json)). In pandas It's achieved using `to_json` with `orient='records'` and `lines=True`. But `to_json` doesn't have the option to use `mode='a'` to append to a file, this PR aims to provide a simple append mode for jsonlines using pandas.

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- [X] closes #35849
- [X] tests added / passed
- [X] passes `black pandas`
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry