Include information on GitHub runners setup in README.MD

[pdewilde]

The "build" job in the ci.yml workflow uses a special group "Beefy" to run on, which behind the scenes is a GitHub large runner group (before adding larger runners, this step took over 5 minutes).

If this repo is forked, that step will hang as no "Beefy" runner group will exist. Documentation should describe how to make your own "Beefy" group, or that you can switch back to "ubuntu-latest" to use a default runner.

[sethvargo]

Alternative option: can runs-on accept dynamic input? For example, would the following work:

jobs:
  do-something:
    runs-on: '${{ vars.runner || "ubuntu-latest" }}'

[pdewilde]

I had been looking into that earlier and it seemed like the answer was "no", but now using a different search term the answer seems to be "yes".

If we can do dynamic input, that is absolutely the way to go. I would recommend vars.build_runner since the runner argument is only used for the build step.

[sethvargo]

I believe you can do it with vars and secrets, but not with env? I don't have a strong opinion on the name, but it would be great if there was a default fallback.

My initial suggestion was going to be "use this really complicated expression that checks whether the org == "abcxyz" and then do something else if it's not", but that felt really bad.