Reset STEP to 0 and fix YAML files

[sinsukehlab]

• Reset STEP to 0
• Fix YAML conditional expressions
• Use skills/action-update-step@v1
• Delete 'close' in <details id=1>
• Some minor changes

Why:

Closes #7

What's being changed:

First, I reverted 51da327 to reset STEP to 0. Then I fixed YAML files so that the GitHub Actions workflows can function as expected. I also edited the 'Update to step n' steps.

Check off the following:

• [x] For workflow changes, I have verified the Actions workflows function as expected.
• [x] For content changes, I have reviewed the style guide.

[sinsukehlab]

@andyfeller Thank you for your approval. I would greatly appreciate it if you could merge this PR.