fix bug 1070942 - add a contribute.json file

I think we should include reopened bugs in this list. We can use <a href="https://bugzilla.mozilla.org/buglist.cgi?list_id=11220394&query_format=advanced&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=REOPENED&product=Mozilla%20Developer%20Network">this URL</a> to do that.