Create alert for `deploy preview` and `build` command failure in #notify-websites channel on Cal-ITP Slack

[leelas-pm]

As a product manager for Cal-ITP websites, I want to be alerted to any preview and deployment failures for content published on either Calitp.org or Mobimart as quickly as possible, in a public channel where others can be tagged in to assist.

To ensure the dev and product team are properly alerted to any deploy preview and build command failures, set up an alert to go to the #notify-websites channel when the command fails to deploy in production.

[machikoyasuda]

Adding: We also want to know when a branch's deploy preview's deploy fails.