Create simple json target

[jonnyeqt]

Description

Simple JSON target for emitting the entities and relations as json objects.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• [?] This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR

[datnguye]

Thanks @jonnyeqt for raising the PR!

I have a couple questions / comments please help to check out:

• Can I ask for the use case of this JSON output?
• Shall we include ALL attributes, e.g. table.description?
• You should run poe format command to format your code and push another commit
• Can you help to update the docs/ folder as well?