add docs

README.md

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+# [Listmonk](https://listmonk.app/)
+
+[Listmonk](https://listmonk.app/) is a tool for e-mail campaigns and newsletters. [Source on GitHub](https://github.com/knadh/listmonk)
+
+<!-- metadata -->
+* **Category**: Development
+* **Status**: 1, alpha
+* **Image**: [`listmonk/listmonk`](https://hub.docker.com/r/listmonk/listmonk/), 2, upstream
+* **Healthcheck**: No
+* **Backups**: No
+* **Email**: ?
+* **Tests**: 2
+* **SSO**: No
+<!-- endmetadata -->
+
+## Basic usage
+
+1. Set up Docker Swarm and [`abra`][abra]
+2. Deploy [`coop-cloud/traefik`][cc-traefik]
+3. `abra app new listmonk --secrets` (optionally with `--pass` if you'd like
+   to save secrets in `pass`)
+4. `abra app YOURAPPDOMAIN config` - be sure to change `$DOMAIN` to something that resolves to your Docker swarm box. Nothing to change apart from the DOMAIN at the moment.
+5. `abra app YOURAPPDOMAIN deploy`
+