CCOC-181 - Aggregate public documentation on README

[marcelovicentegc]

What is the purpose of this pull request?

To aggregate the public documentation available for this system on the README. Specifically, to move the GraphQL directives docs from Notion, here, to later "deprecate" (or simply point from the Notion document to this README) that Notion document.

What problem is this solving?

We have documented this system on Notion, the Internal Docs, and the README. The problem this PR is solving is to tie these references up and make it easier to navigate between this systems' documentation.

Types of changes

• [ ] Bug fix (a non-breaking change that fixes an issue)
• [ ] New feature (a non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] Requires change to documentation, which has been updated accordingly.