Add #django-dev IRC channel information to "Contributing to Django" page

[Kenneth Yang]

Currently, according to the ​Google Group Discussion page, the only mention for this channel is on the ​Code of Conduct FAQ page, but it should also be mentioned on the ​Contributing to Django page.

The source for the "Contributing to Django" page is found here: ​https://github.com/django/django/blob/master/docs/internals/contributing/index.txt

[Augusto Goulart]

That sounds really good to me.

I believe that most of the newcomers interested in contributing to Django doesn't even know that ​irc://irc.freenode.net/django-dev exists.

[Tim Graham]

There are a few mentions but mentioning it on the contributing index would be fine.

$ grep -rI "#django-dev" *
internals/contributing/new-contributors.txt:   `#django-dev` IRC channel.
intro/contributing.txt:    to |django-developers| or drop by `#django-dev on irc.freenode.net`__ to

[Augusto Goulart]

I was thinking about something, along the lines of:

Join the django-developers mailing list and share your ideas for how to improve Django. We’re always open to suggestions. You can also interact via the #django-dev IRC channel.

To avoid creating another topic just for the #django-dev IRC.

[Tim Graham]

Looks good.

[Kenneth Yang]

Hi Augusto,
Would you mind if I claim this ticket for myself and make the fix that you proposed?

[Augusto Goulart]

Hi Kenneth.
Absolutely not. Go ahead and submit your patch.

[Kenneth Yang]

Thank you very much!

[Kenneth Yang]

​PR

[Tim Graham <timograham@…>]

In 5d022eae:

Fixed #29369 -- Mentioned the #django-dev IRC channel in contributing index.

[Tim Graham <timograham@…>]

In 4329bd7a:

[2.0.x] Fixed #29369 -- Mentioned the #django-dev IRC channel in contributing index.

Backport of 5d022eae747b9e6432cea4fe5e6e87cd8e627141 from master