It can be frustrating after you push the changes you made to `.gitlab-ci.yml`, only to discover later that it's invalid on gitlab.com. Here's how to verify/lint the config.
Login to GitLab.com and navigate to any of your repo or project. It must be under your account. If you don't have one, simply create a new project or fork one.
Simply add `/-/ci/lint` to the end of your repo link and navigate to that link.