Use bash github actions to (cross-)post to dev.to

I want to start a series a tutorial about Gwion,
It should be part of Gwion's doc.
as well as available on dev.to,

devto.sh is a part of this process,
the one that takes a directory of markdown files and publishes the content to dev.to.

It is a both a github action
and a template,
so it should be easy for anyone to reuse 😄

EDIT: looks like we can add tags