Mark steps as optional and project_key as mandatory

Author: leplatrem

README.md

@@ -76,10 +76,10 @@ to the Bugzilla ticket on the Jira issue.
 
 **Parameters**
 
-- `jira_project_key`
+- `jira_project_key` (**mandatory**)
     - string
     - The Jira project identifier
-- `steps`
+- `steps` (optional)
     - mapping [str, list[str]]
     - If defined, the specified steps are executed. The group of steps listed under `new` are executed when a Bugzilla event occurs on a ticket that is unknown to Jira. The steps under `existing`, when the Bugzilla ticket is already linked to a Jira issue. The steps under `comment` when a comment is posted on a linked Bugzilla ticket.
     If one of these groups is not specified, the default steps will be used.