Add configuration to use a private registry instead of docker.com when running as the yq action

[rseeton]

When running the yq action in GitHub we encounter the following message:

Pull down action image 'mikefarah/yq:4-githubaction'
/usr/local/bin/docker pull mikefarah/yq:4-githubaction
Error response from daemon: toomanyrequests: You have reached your unauthenticated pull rate limit. https://www.docker.com/increase-rate-limit
Warning: Docker pull failed with exit code 1, back off 4.362 seconds before retry.

We run a local private registry (Artifactory) which caches images from the Docker.com registry (this allows us to do one pull from docker and then to serve it to multiple users internally).

To make this work, we need the ability to redirect the image source - an example can be seen here:

docker/setup-buildx-action#375

[mikefarah]

Sorry I'm not quite sure what I'd need to do to support that - need to do more reading when I have time. Otherwise happy to accept a PR

[rseeton]

@mikefarah - No worries and certainly no rush (As a work around we are installing yq as part of the Github instead of using the action).

Let me take a look and see if I can get you a PR.