Add mastodon-redis role

roles/mastodon-redis/tasks/main.yml

@@ -0,0 +1,8 @@
+---
+# This playbook installs Redis for Mastodon's user
+
+- name: Install redis
+  apt: name={{ item }} state=latest update_cache=yes
+  with_items:
+     - redis
+     - redis-server

site.yml

@@ -6,3 +6,4 @@
     - ruby
     - mastodon-app
     - mastodon-postgresql
+    - mastodon-redis