Improve example jobs in README.md

[guyzyl]

Improve the example jobs in README.md by:

• Making the job fail if one of the steps fails
• Show ✅/❌instead of success/failure to make it easier to see if and which step failed

This is what it looks like:

[cspollar]

This is a nice improvement - just added a version of it to one of my repos. If someone wants to get really fancy - I'd love to see an example that uses GITHUB_STEP_SUMMARY.

Edit: Adding a GITHUB_STEP_SUMMARY was relatively easy. Although, I had to add line breaks between the heading lines in output (markdown, can be finicky).

 // 5. Update GITHUB_STEP_SUMMARY
await core.summary
    .addHeading('Results')
    .addRaw(output)
    .write()