Fixed #14401 -- Added a contributing howto guide for new users. Thank you to…

Fixed #14401 -- Added a contributing howto guide for new users. Thank you to everyone who added their advice, feedback, and wisdom to the wiki article while constructing this new guide.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15645 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/howto/index.txt

@@ -11,6 +11,7 @@ you quickly accomplish common tasks.
 
    apache-auth
    auth-remote-user
+   contribute
    custom-management-commands
    custom-model-fields
    custom-template-tags