Add pictrs to ansible.

ansible/templates/config.hjson

@@ -20,6 +20,8 @@
   jwt_secret: "{{ jwt_password }}"
   # whether tls is required for activitypub. only disable this for debugging, never for producion.
   tls_enabled: true
+  # address where pictrs is available
+  pictrs_url: "http://pictrs:8080"
   # email sending configuration
   email: {
     # hostname of the smtp server