Get cowsay version in to man page

I'd like the cowsay.1 man page to include the version of cowsay. And not the date the man page was generated. I'm not sure how to do this. The `cowsay.adoc` file has a `:man version:` attribute, but it doesn't seem to be used, and per the [asciidoctor man-making doco](https://docs.asciidoctor.org/asciidoctor/latest/manpage-backend/#document-attributes), that doesn't look like the right thing. Pretty sure this can be done. Asciidoctor's own `man asciidoctor` has the version in it. <img width="933" alt="image" src="https://github.com/user-attachments/assets/89fbaf4c-46f1-47d0-be28-a5393d1fb3fe"> It uses a `:release-version:` attribute. ``` = asciidoctor(1) Dan Allen; Sarah White :doctype: manpage :release-version: 2.0.23 :man manual: Asciidoctor Manual :man source: Asciidoctor {release-version} ifdef::backend-manpage[:!author:] ``` But I tried adding `:release-version: 3.8.5-SNAPSHOT` to cowsay.adoc, and it had no effect. The Asciidoctor man page `.adoc` and their doco are using a different markup format that we are. Don't know if that's significant.