Plugin is probably not the best word. But since iOS supports content blockers, I was imagining it’s possible to have dedicated apps block reddit pop-ups.
It would be most useful to do this in a dynamic way though. I might actually want to know that examplewebsite.com has an app that I could download. But once I've gone to that site 5 times, then the banner should be hidden. Either I don't want the app, or I've already downloaded it. Unfortunately, I don't think content blockers can include any logic like this.