Validate the action and action-version exists in workflows

[award28]

Background

The action-validator should validate that any actions in the - use: {action}@{version} format exist. If this is not the case, an error should be reported.

Scope of Work

• When validating an action step, if the action step has the uses key, validate that the action and specific version exist in GitHub.
  • If this is not the case, throw an error.

[award28]

I'll start looking into this issue and add any details that I come across. Would be happy to raise a PR for this one.

[mpalmer]

This would certainly be an interesting additional validation. My only reservation is that it would presumably slow down validation a bit because of the network calls. Putting it behind a flag (something like --remote-checks perhaps) would work around that concern.

I'd love to take a look at a PR when you've got one together.

[award28]

@mpalmer The PR for this issue is ready for review when you have the time