Build Scratch-Based Docker Images

[BrenekH]

It would be advantageous to build a runner docker image that doesn't rely on a package manager to download FFmpeg.

A possible source of these binaries could be https://johnvansickle.com/ffmpeg/, but the licensing needs to be looked at. I assume it'd be fine to download using curl or wget and put into a docker image, but I'm not 100% on that just yet.

[BrenekH]

Currently, the runner-scratch-image branch contains the changes to the Dockerfile and GitHub Actions workflow that make a scratch image possible. I have confirmed that they work as intended (including timezone related items such as logging).

Even though everything is operating correctly there are still questions that need to be answered, the foremost being, is it legal to distribute FFmpeg in this way? Encodarr is licensed under MPL 2.0, but FFmpeg is either LGPL or GPL which may pose a problem when packaging everything together into a Docker image. The other issue is how will hardware acceleration be accomplished because it appears that John Van Sickle's builds don't support it.