add weekly job for regendoc updates

[pfctdayelise]

Travis has cron jobs. It would be useful to set a weekly job to verify the docs examples are up to date.

I emailed travis support to ask this feature to be enabled for the pytest repo. Once it is enabled maybe Ronny can help setting up the job.

[pfctdayelise]

It's enabled now. I got this response from travis:

I've just enabled Cron Jobs for the pytest-dev organization.

Details on how to use them are in: https://docs.travis-ci.com/user/cron-jobs/

It's a beta feature at the moment, so please let us how it goes and if there's anything you feel can be improved or anything you miss.

[asottile]

we can do this with github actions scheduled runs now as well