Does this only work with organization projects?

I noticed in the readme that you have a parameter `organization`. I wanted to use this for a personal project board I had, which is not under any org. When unspecified, it defaults to my username (`cp2004`) however the action seems to fail.

The error also seems to indicate organization-only:
> `gh: Could not resolve to an Organization with the login of 'cp2004'.`

https://github.com/cp2004/github_management/runs/7776329997?check_suite_focus=true#step:4:65

Is that the case or have I broken it? If that is the case, would you consider making it work with both *or* putting it in the readme?

This [add to project](https://github.com/actions/add-to-project) action allows to specify the URL, rather than separating the org/project ids, and it works OK.