One additional maintainer wanted

Hey,

This project covers all the use-cases of ePages GmbH for quite some time already and I'm the sole maintainer atm.
Since there is great outside interest in and dependence on this project, since there's a low truck factor, it would be nice to have an additional maintainer from the [contributors so far](https://github.com/ePages-de/restdocs-api-spec/graphs/contributors).

Main work to be done and privileges gained:

* Active in discussions in the GH issues
* Review + merge PRs
* Keep master build green
* Tag + draft releases

[The release process is not 100% automated, yet. Drafting a release on GH ultimately results in artifacts in Sonatype, which need to be manually closed+released there (negligible effort of ~5min per release)](https://github.com/ePages-de/restdocs-api-spec/#maintenance) by either me (@ooz @ozscheyge ) or @jmewes .