add explanation how we add new runners to our gitlab ci setup
add explanation how we add new runners to our gitlab ci setup

gitlabhq/gitlab-ci-runner,mfittko/gitlab-ci-runner,andrewmunsell/gitlab-ci-runner,gitlabhq/gitlab-ci-runner,andrewmunsell/gitlab-ci-runner,cui-liqiang/gitlab-ci-runner,mfittko/gitlab-ci-runner,cui-liqiang/gitlab-ci-runner