Add OrgReader

[RomainGehrig]

Description

This is a draft PR to add an Org mode reader that can create documents at different heading depths. (It's not uncommon for Org users to have more than 5 levels of headings). I still need to add unit tests and go through the checklist.

Type of Change

• New Loader/Tool for Org files

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Added new unit/integration tests
• Added new notebook (that tests end-to-end)
• I stared at the code and made sure it makes sense

Suggested Checklist:

• I have added a library.json file if a new loader/tool was added
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran make format; make lint to appease the lint gods

[elsatch]

I am totally mind blown! I started working yesterday on a OrgmodeReader, created the base structure, init... then came back to check the status of a PR... then discovered your PR. Tears of joy are about to happen!

Thanks so much for putting this up!