Github action for publishing to DITA-OT registry

## Description
When releasing a new version of a plugin I want to automatically add it to the DITA-OT registry. It would be nice if this could be done automatically. If this would be possible, it would be even nicer to read in the docs how this works. Currently, this takes some effort (cloning, hashing, pull request, ...).

## Possible Solution
It would be nice if this could be done automatically using Github Actions. If this would be possible, it would be even nicer to read in the docs how this works.