remove docs, add README

Author: jwulf

docs/README.md

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+# Documentation
+
+API documentation can be found on the [`gh-pages`](https://github.com/creditsenseau/zeebe-client-node-js/tree/gh-pages) branch.
+
+It is automatically generated in CI, and is published [here](https://creditsenseau.github.io/zeebe-client-node-js/).