There is no plugin that I know of that does this. It’s possible to do, yes, but to be quite honest, getting these prompts right for all users is tricky. Some users may find them annoying, it can disrupt their workflows, interrupt, etc.
In Discourse core, you have some other, simpler options:
you could pin the tips topic in a specific category or globally, so that people can more easily find it
you can add a link to it from the sidebar, for all users (though I see your site doesn’t have a sidebar)
you could post each tip, on a schedule, as a separate topic – that will also encourage discussion around each one