Add option to use GitHub Statuses instead of a comment

[dcastil]

It would be awesome if I could choose to use GitHub Statuses instead of a comment to post the size limit information. That would make it a lot easier to see how the size limit changed between commits in a PR and make it more obvious to which commit a size-limit report belongs.

I've seen in #25 (review) that the idea came up already and it is also used in the bundlesize package. I also think it should be possible to do right from the GitHub action without the need for a GitHub app as github-status-action can also submit a status just with the secrets.GITHUB_TOKEN.