Add role variables to readme

README.md

@@ -12,6 +12,28 @@ This role requires Ansible 2.0 or higher.
 Role Variables
 --------------
 
+```gitlab_runner_concurrent```
+The maximum number of jobs to run concurrently.
+Defaults to the number of processor cores.
+
+```gitlab_runner_coordinator_url```
+The GitLab coordinator URL.
+Defaults to ```https://gitlab.com/ci```.
+
+```gitlab_runner_registration_token```
+The GitLab registration token.
+
+```gitlab_runner_description```
+The description of the runner.
+Defaults to the hostname.
+
+```gitlab_runner_executor```
+The executor used by the runner.
+Defaults to ```shell```.
+
+```gitlab_runner_tags```
+The tags assigned to the runner,
+Defaults to an empty list.
 
 Dependencies
 ------------