How to cache Docker images and reduce Hub calls in CI/CD

What this post added

This post introduces and details the implementation of a Docker Hub registry mirror to address Docker's new pull rate limits. It provides instructions for self-hosted GitLab Runners on how to set up and configure a Docker registry mirror, including Docker commands and `daemon.json` configuration. It also mentions the use of Google's Docker Hub images mirror for GitLab.com Shared Runners and briefly touches upon alternatives like authentication.