add a contribute.json file (bug 1074452)

I did my best to find all the data to populate the json file, but l'm assuming I'll need to make a change or two. 
Repeating what I've said in another comment that is now hidden: 

To be honest I am not sure we need this view at all. Maybe we could just have nginx serve the file directly. There is nothing dynamic in there so there is no point of having django do it.