Autoscale GitLab CI/CD runners and save 90% on EC2 costs

What this post added

This post details the implementation of an autoscaling GitLab CI/CD runner setup using docker-machine and AWS EC2 Spot Instances. It covers the creation of a spawner machine, installation of gitlab-runner and docker-machine, and configuration of the `config.toml` file to enable autoscaling. Key `MachineOptions` for AWS EC2, including VPC, region, instance type, and the use of `amazonec2-request-spot-instance=true` with `amazonec2-spot-price` to leverage cost savings from Spot Instances, are explained.