added config data_dir (else in ~, which isn't set)

roles/matrix-bridge-mautrix-signal/templates/config.yaml.j2

@@ -73,6 +73,8 @@ signal:
     outgoing_attachment_dir: /signald/attachments
     # Directory where signald stores avatars for groups.
     avatar_dir: /signald/avatars
+    # Directory where signald stores auth data. Used to delete data when logging out.
+    data_dir: /signald/data
     # Whether or not message attachments should be removed from disk after they're bridged.
     remove_file_after_handling: true