added noise automation

roles/account-automation-backend-noise/README.md

+This role installs
+[ai-scripts](https://git.autistici.org/ai/ai-scripts) cron jobs that
+are associated with the *noise* service and run on the *backend* nodes.
+
+These include the *create* script.
+

roles/account-automation-backend-noise/meta/main.yml

+---
+dependencies:
+  - { role: account-automation-backend }
+  - role: account-automation-cron
+    vars:
+      scripts:
+        - name: create-newsletters
+          calendar: "*:3"

roles/noise/meta/main.yml

+---
+dependencies:
+  - { role: account-automation-backend-noise }
+