Add documentation of variables

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

roles/matrix-cactus-comments/defaults/main.yml

@@ -29,7 +29,14 @@ matrix_cactus_comments_version: latest
 matrix_cactus_comments_docker_image: "{{ matrix_container_global_registry_prefix }}cactuscomments/cactus-appservice:{{ matrix_cactus_comments_version }}"
 matrix_cactus_comments_docker_image_force_pull: "{{ matrix_cactus_comments_docker_image.endswith(':latest') }}"
 
+# matrix_cactus_comments_client_version specifies the version of the cactus-client release to use.
+# For available versions, see: https://gitlab.com/cactus-comments/cactus-client/-/releases
+# Also see: `matrix_cactus_comments_client_local_dir`
 matrix_cactus_comments_client_version: "0.13.0"
+
+# matrix_cactus_comments_client_local_dir specifies a local directory (on the Ansible controller, not on the remote server) with cactus-client files to use.
+# This is an alternative to `matrix_cactus_comments_client_version`, to be used when you'd like to
+# provide the files locally / manually.
 matrix_cactus_comments_client_local_dir: ''
 
 matrix_cactus_comments_client_endpoint: "/cactus-comments/"