add config file for PullRequest bot automation

[xtremerui]

This just simply adding a configuration file for this (bot)[https://github.com/xtremerui/auto-pr-team/blob/master/index.js] so an owner of a pull-request against concourse/concourse could be added to concourse org contributor team.

[jamieklassen]

I kinda want the team name to be 'Contributors' instead of 'Contributor' since other team names are plural (like Alumni & Developers), but it would take coordinating against concourse/hush-house#127, so I'm not fussed. Otherwise, based on:

https://github.com/xtremerui/auto-pr-team/blob/13315a8aa7833d03596f784c12e29502ce1c15bc/index.js#L23-L32

it seems like this will be a no-op until a 'contributor' team is created, right? Let's not forget to create it.

[xtremerui]

Good point lets go with contributors. Though I don't have the permission to create the team under concourse org. Neither can I accept the request of adding the auto_pr_team bot to concourse/concourse repo.

[jamieklassen]

It looks like the bot is already integrated:

EDIT: I also created https://github.com/orgs/concourse/teams/contributors