Add notes on how you can help to contributing documentation

[joshsmith]

I wanted to clarify further how someone new to the project could help. This is my first stab at it.

[joaomdmoura]

👍

[joshsmith]

@joaomdmoura no issues with this at all?

[joaomdmoura]

@joshsmith It sounds great me. There some details that we can add, but it's complementary:

If you want, you can also mention that anyone should feel comfortable to create issues that aim to discuss ideas / problems or implementations.

There are some other specific hints like, squash commits when open a big PR, write tests and always rebase master

[joshsmith]

All great ideas. Let me change my PR.

[joshsmith]

@joaomdmoura Implemented your suggestions. If you have any more, let me know. Otherwise you can always feel free to open an issue about it.