High-level diagram visualization of the dropbox-sdk-python codebase

[ivanmilevtues]

This PR introduces markdown (mermaid) documentation in order for new people to get up-to-speed faster. You can see how the docs render here: https://github.com/CodeBoarding/GeneratedOnBoardings/blob/main/dropbox-sdk-python/on_boarding.md

The idea behind the change is to help people get up-to-speed with the codebase faster and more asynchroniously. I would love to hear what is the current process in dropbox for on-boarding, what do you think of diagram first documentation and in what ways we might be able to help to improve the process!

The way the generation works at the moment is via Static Analysis and LLMs. The idea is that people can generate a new one as often as there are changes and so you get always up-to-date docs.

Any sort of feedback is more than welcome, especially on the quality of the diagrams!

Full disclosure: we're trying to turn this into a startup, but we're still in a very early stage and figuring out what will actually be useful for people.

Checklist

General Contributing

• [x] Have you read the Code of Conduct and signed the CLA?

Is This a Code Change?

• [x] Non-code related change (markdown/git settings etc)
• [ ] SDK Code Change
• [ ] Example/Test Code Change

Validation

• [x] Does tox pass?
• [x] Do the tests pass?