release as hugo module

**Is your feature request related to a problem? Please describe.**
Hugo suggests to use [modules](https://gohugo.io/hugo-modules/use-modules/) instead of git sub modules

**Describe the solution you'd like**
Release as module, e.g. [docsy](https://github.com/google/docsy/blob/main/go.mod)

**Describe alternatives you've considered**
Write a guide for my documentation editor with instructions to clone with sub module in mind

**Additional context**
Initialize a [hugo module](https://gohugo.io/hugo-modules/use-modules/#article)