fix: use GITHUB_OUTPUT instead of deprecated set-output command

[suzuki-shunsuke]

• https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/
• https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter

set-output was deprecated.

AS IS

echo '::set-output name={name}::{value}'

TO BE

echo "{name}={value}" >> $GITHUB_OUTPUT

[ianlewis]

Updates #1004

[suzuki-shunsuke]

I thought github.com/sethvargo/go-githubactions is useful because this library has already migrated to GITHUB_OUTPUT in v1.1.0, but I found the proposal was rejected. #153

[ianlewis]

Yeah, I think it's a useful library as well but I think we would only be using it for reading the context and setting outputs so it's not really worth adding another dependency.

[suzuki-shunsuke]

Yeah, I agree.