Support authentication when checking links

[ryanwinter]

Is your feature request related to a problem? Please describe.
I have run this using a private repo (not going public for a few months) and it fails all link checks again the internal repository itself.

Describe the solution you'd like
Add the ability to set an authorization token on the link check. This would give the ability to pass a personal access token to the action.

Describe alternatives you've considered
Unsure if there is an alternative

[pwalleni]

Yes, please. Resources protected by authentication may cause the server to return 404 to linkspector. We want to check if the protected resource exists to ensure the link works when authenticated users click it. We can add 404 to the list of aliveStatusCodes, but it's not a great workaround.