Allow starting of container if foundryvtt.com is down, and release zip has already been downloaded

[cs96and]

🚀 Feature Proposal

foundryvtt.com went down for a few minutes earlier today, at the same time that I was trying to bring my container up. The container failed to authenticate and gave up.

The release zip had already been downloaded from a previous run, and was in the cache, so it could have just carried on with the cached one.

[felddy]

This makes sense.

I think the behavior you are looking for is the same as if FOUNDRY_USERNAME and/or FOUNDRY_PASSWORD are not specified. As documented here: https://github.com/felddy/foundryvtt-docker#required-combinations

So if authentication fails all is not lost. We can still fail forward to the cache.