Add support for application/json mime type in statement output

[Strunevskiy]

Description

It adds support for application/json mime type in statement output since Livy PySpark kind has %json magic command which return json with application/json mime type in statement output

Checklist

• [X] Wrote a description of my changes above
• [X] Formatted my code with black
• [X] Added a bullet point for my changes to the top of the CHANGELOG.md file
• [X] Added or modified unit tests to reflect my changes
• [X] Manually tested with a notebook
• [N/A] If adding a feature, there is an example notebook and/or documentation in the README.md file

[Strunevskiy]

@devstein could I ask you review this PR ?