Improve the web accessibility

[vanessametonini]

I am member of a working group of web accessibility here in Brazil, and we are moving our repositories to Github, and we need to have an accessible Git tutorial. So, we like a lot of this tutorial and we want to contribute on it to improve the acessibility on it. But I believe that to do it in the best way, we need first to be concentrated in one "html" file, and because of it I also suggested the improvement of the translation files. What do you think?