Containerize a GitHub Actions self-hosted runner

• Install Docker
• Install sysbox
• Add sysbox as the default runtime

References

• https://baccini-al.medium.com/how-to-containerize-a-github-actions-self-hosted-runner-5994cc08b9fb
• https://github.com/beikeni/github-runner-dockerfile
• https://github.com/nestybox/sysbox#installing-sysbox
• https://github.com/PasseiDireto/gh-runner
• https://github.com/nestybox/sysbox/blob/master/docs/user-guide/install-package.md
• https://github.com/nestybox/sysbox/blob/master/docs/user-guide/install-package.md#configuring-dockers-default-runtime-to-sysbox