Docs feedback: shfmt section is outdated

This page remarks that shfmt cannot be used with a GitLab Runner, due to the official Docker image being too limited. According to this comment, this has now been resolved with the addition of an Alpine Linux variant of the image. I have had success with using this in my GitLab CI configuration using something like this:

shfmt:
  stage: test
  image: mvdan/shfmt:latest-alpine
  script:
    - shfmt -d .