[RFC] Post/tutorial for newcomers

Hi, everyone

I've been writing a blog post based on what I learned during GSoC to help other students here at FLUSP[1] start contributing as well.

In the meantime `Documentation/MyFirstContribution.txt` was released, so I've pointed my interested colleagues to it. But since I was already pretty close to finishing the post, I decided to conclude it anyway.

Here is the end result: https://matheustavares.gitlab.io/posts/first-steps-contributing-to-git If you have any comments or suggestions for it, please, let me know :)

Thanks, Matheus

[1]: https://flusp.ime.usp.br