Requests: Maybe look at blocking registration of usernames containing words on that list? Or a separate list (e.g. you might want to block someone from registering with admin in their name, but not restrict someone from writing admin in their post).
As for moderator emails, I wouldn't do that (because you could cause a site to be tagged a spammer by submitting multiple posts with filtered words on purpose and triggering emails). It'd be better to inform users as they try to post instead with a red error bar, and not let the post be submitted. Or tap into the Approval mod to auto-unapprove any post that the filter flags, Flag it and let moderators choose to approve it or delete it.
Btw, you should also require flarum-ext-flags in your composer.json if you're going to use Flags.
EDIT (and quoting to save time and properly source my answer):
You might want to check that Approval and Flags are enabled before calling their actions, too, just to stop errors.
