Support for GitHub Enterprise Server

[posquit0]

When I tried to use srvaroa/labeler action in GitHub Server, I got the error message like below.

GET https://api.github.com/repos/${my-org}/${my-repo}/contents/.github/labeler.yaml?ref=xxxxxxxxxxx: 401 Bad credentials []

I think that configuration for GITHUB_API_HOST is need to support GitHub Enterprise Server.