GHA: Slack us if Docker build or rendering fails

[jaclyn-taroni]

Purpose

Sometimes rendering or pushing to Dockerhub fails and we don't know about it. This adds steps to those two workflows per the instructions posted: https://github.com/AlexsLemonade/refinebio-examples/issues/315#issuecomment-717914841

Issue addressed

I'm going to say that this closes #315 but of course this is the kind of thing I couldn't test ahead of time 🤞

Notes for reviewers

• How would we like to test this? Intentionally add something that won't build to the Dockerfile?
• The action we're using looks a-okay to me, but another pair of 👀 would be helpful (this is tied to the commit for the tag I'm using): https://github.com/ravsamhq/notify-slack-action/tree/d91b0d897737030128964a7d274248dda13a6e3f

[jashapiro]

This looks fine to me. Will it report the step that failed? Probably not, but easy enough to go look, which we would want anyway.

Here is how I would test it:

Add jaclyn-taroni/render-fail-loudly to the branch list:

on:
  push:
    branches: [ staging, master, jaclyn-taroni/render-fail-loudly ]

This will make it run with every push to your current branch.

Then create something that makes things fail. I suggest typos as the simplest option, but trying to load a missing library is another good option (an error we don't explicitly deal with).

If I see an error in Slack, and if I then see the error-inducing commit reverted, I will approve.