This is an addition to this PR: https://github.com/ctran/annotate_models/pull/692
I've seen it's been stale for a while and it's rather simple fix.

I noticed my ActiveAdmin resources are not being annotated.
I know ActiveAdmin uses plural model names, but, as far as I remember, they used to use singular model names in the past.

We can see some "evidence" of that here: https://activeadmin.info/2-resource-customization.html#customizing-parent-menu-items
Probably in other places as well.

In order to keep the gem working as expected for singular ActiveAdmin resources, I suggest we annotate both singular and plural model names.

I just tested this out in a project of mine where I renamed one file to be in singular form and left the other files in plural form.
It worked like a charm. :)