Consider including *some* event handlers by default

### Issue Details The fact that `on <event> …` syntax is included in Caddyfiles by default but there's no built-in way to handle it is… kind of very weird. Like, given the [sheer simplicity](https://github.com/mholt/caddy-events-exec/blob/master/module.go) of the one recommended by the project, it feels weird that it's not built into caddy by default. Like, I agree that xcaddy makes adding in more complicated modules easy, but the fact that just running a command on events by default *isn't* included means that you can't take a system that has installed caddy via a package manager and have it respond to events at all, only have them emitted in the logs. It feels like this is a relatively low-hanging fruit that could be potentially fixed. ### Assistance Disclosure AI not used ### If AI was used, describe the extent to which it was used. _No response_