Add readlater/wallabag default vars to role

roles/readlater/defaults/main.yml

+secret_root: '{{ inventory_dir | realpath }}'
+secret_name: 'secret'
+secret: '{{ secret_root + "/" + secret_name }}'
+
+wallabag_version: 1.9.1
+wallabag_domain: "read.{{ domain }}"
+wallabag_salt: "{{ lookup('password', secret + '/' + 'wallabag_salt', length=32) }}"
+wallabag_db_username: wallabag
+wallabag_db_password: "{{ lookup('password', secret + '/' + 'wallabag_db_password', length=32) }}"
+wallabag_db_database: wallabag