add some documentation in README.md

roles/dehydrated-domains/README.md

@@ -0,0 +1,17 @@
+# Dehydrated Domains
+
+Ansible role to configure domains for use with dehydrated
+
+## Usage
+
+```yaml
+vars:
+    dehydrated_domains:
+        name: example.com
+        deploy_challenge_hook: printf 'server 127.0.0.1\nupdate add _acme-challenge.%s 300 IN TXT "%s"\nsend\n' "${DOMAIN}" "${TOKEN_VALUE}" | nsupdate -k /var/run/named/session.key
+        clean_challenge_hook: printf 'server 127.0.0.1\nupdate delete _acme-challenge.%s TXT "%s"\nsend\n' "${DOMAIN}" "${TOKEN_VALUE}" | nsupdate -k /var/run/named/session.key
+
+roles:
+    - role: dehydrated-domains
+
+```