support: destination_dir doesn't play nicely with cname/enable_jekyll

[nex3]

Checklist

• I am using the latest version of this action.
• I have read the latest README and followed the instructions.
• I have read the latest GitHub Actions official documentation and learned the basic spec and concepts.

Describe your question

If you set destination_dir to a directory other than the default root-level directory (such as docs), the action will still put the CNAME and .no_jekyll files at the root of the repository, causing them to be ignored by GitHub pages when that sub-directory is set as the deployment root.

Relevant links

Public repository: https://github.com/sass/sass-site/tree/cd3443d2940b1925001e9627ed05c765247235ed
YAML config: https://github.com/sass/sass-site/blob/cd3443d2940b1925001e9627ed05c765247235ed/.github/workflows/ci.yml
YAML workflow: https://github.com/sass/sass-site/runs/6601995954

Relevant log output

No response

Additional context.

No response

[peaceiris]

What is your purpose in the setting destination_dir: docs? Why don't you deploy the root directory of the gh-pages branch? Deploying /docs is an old way.