For example, we could automatically add CSS classes to the <body> tag for all experiments that are running, which developers could key in to at little cost. This would be a generalization of what @mpopov@wikimedia.org just proposed to Web at https://miro.com/app/board/uXjVMtGrgVc=/?moveToWidget=3458764620892974416&cot=14
TODO: Sam adds details about implementation :) (mostly copying the code from Mikhail's design above ^)
NOTE: this task shall be used as an opportunity to build bridges with folks using this platform.