Add missing heading for steps.working-directory (#28613)

Co-authored-by: Siara <108543037+SiaraMist@users.noreply.github.com>

content/actions/using-workflows/workflow-syntax-for-github-actions.md

@@ -615,6 +615,8 @@ Each `run` keyword represents a new process and shell in the runner environment.
       npm run build
   ```
 
+## `jobs.<job_id>.steps[*].working-directory`
+
 Using the `working-directory` keyword, you can specify the working directory of where to run the command.
 
 ```yaml