docs: add the first ADRs

[MaferMazu]

Description

This PR adds 3 ADRs:

• Purpose of this Repo
• API connection
• Fulfillment and refund

And I slightly changed the index to clarify the supporting info.

I made those changes following the ADR template from the OEP-19: Developer Documentation.

Testing instructions

• Principally, I want you to help me review the content of the documents I edited.
• To see the documentation locally in the browser, you must create a python venv, install the docs.txt requirements, run make html inside the docs directory, and then run python -m http.server 8200 --directory build/html.

Additional information

Screenshot of the index view

Screenshot of the Fulfillment and refund ADR

[openedx-webhooks]

Thanks for the pull request, @MaferMazu! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
• any other information that can help Product understand the context for the PR

All technical communication about the code itself will be done via the GitHub pull request interface. As a reminder, our process documentation is here.

Please let us know once your PR is ready for our review and all tests are green.

[MaferMazu]

@wlvasquez @julianramirez2, can you review this, please? Your insight will be helpful to be sure of the correctness and clarity of the information.

[julianramirez2]

Looks good to me

[wlvasquez]

A few minor grammar and formatting recommendations were added for your consideration.

[MaferMazu]

Thanks @julianramirez2
@wlvasquez, if you have more feedback, let me know :D

[openedx-webhooks]

@MaferMazu 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.