Add Slack app to repo

[sgerogia]

Hello.

We would like to get notifications of upcoming releases.

It would be a massive help if we could do it through Github's Slack integration.

Could you kindly install it?

Thank you

[faddat]

I would actually like to close this and I’m just gonna wait for one more person to agree with that. I really don’t want the Slack app on this repository but thank you