<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=17862) </details> <!--IssueSummary end--> Let's add a CSS linter to make sure all class names are done using dashes and not underscores which will prevent a potentially catastrophic problem like we had last week. For example if it says: `some-class` that is kosher. But `this_is_totally_not_kosher_dude`. cc @stanhu @iamphill @connorshea