Documentation (CONTRIBUTING.md): add commit guide

[avara1986]

Add to contributing this link https://chris.beams.io/posts/git-commit/

[alexppg]

Maybe this is superseded by this, if you like it? #195

[avara1986]

I like commitizen @alexppg but commitizen and this issue both are "recommendations" and can't be "impositions". Add the both ways are useful, what do you think? :)

[alexppg]

Oh well, I see commitizen as a way to standarize the commits. It's not really useful if not everybody uses it, since you won't be able to use it's features.
So if commitizen won't be mandatory, I would just close the issue. This guide is pretty useful anyway!

[avara1986]

No, no. Sorry, maybe i need to check and figure out commitizen. Do you can set commitizen as a mandatory way to commit new changes? I was thinking that is a tool to "help" when you commit anything, not a tool like black that force you to use this way of add changes

[alexppg]

They do have a way to check that the commit follows the stipulated format with cz check. Also they have a pre-commit.

The way it works is that you create a configuration in the root of the project with the format you want and everybody just have to execute git cz and a interactive interface will appear asking questions.

It's not mandatory to use cz as is as long as your commit follows the format. I actually have it only as a git template, I don't use the interactive tool, for example.