Logs errors when GitHub script fails

If an error occurs when calling a GitHub script during a workflow run, the exception is displayed: https://github.com/exercism/org-wide-files/runs/6383394202?check_suite_focus=true

However, this is fairly unhelpful, as the actual error is hidden inside the response's `data.errors` array:

```json
response: {
...,
data: {
message: 'Validation Failed',
errors: [Array],
documentation_url: 'https://docs.github.com/rest/reference/pulls#create-a-pull-request'
}
},
```

It would be super helpful if we could show the actual error messages, likely output as errors via https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-error-message