As discussed in #2133, contribution guidelines are hard to find.
This PR is an attempt to ease the process by giving newcomer friendly advices and some more insight on the contribution process for Nit.
@tonygaetani, do you think a document like this one would have been helpful for you ? Is there anything you would change to make it friendlier/clearer ?
Close #2133
Pull-Request: #2134
Reviewed-by: Jean Privat <jean@pryen.org>