Add miniflux deployment

Contains default credentials but these should be overwritten with
group or host -destined variables.

Add default credentials

Hide real credential files from git

roles/miniflux/README.md

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+# miniflux
+
+A minimalist rss feed reader.
+Deployed in a docker swarm with caddy.
+
+## Defaults
+
+```
+miniflux_upstream_file_dir: "{{ docker_stack_files_dir }}/{{ stack_name }}"
+```
+
+The on-target directory where the proxy configuration file should be stashed.
+
+```
+miniflux_use_https: true
+```
+
+Whether the service should be reachable through http (port 80) or through https (port 443) and provision an https certificate. Usually you will want this to stay `true`.
+
+```
+miniflux_version: latest
+```
+
+The docker image version to be used in stack creation.
+
+```
+subdomain_alias: rss
+```
+
+If the deployed container should be served over a uri that is not the stack name. 
+By default, it will be set to `rss.yourdomain.com` - 
+if this option is not set it will be served on `miniflux.yourdomain.com` instead.