Include 'shell command' as a possible step task (#2211)

Co-authored-by: Lucas Costi <lucascosti@users.noreply.github.com>

content/actions/learn-github-actions/introduction-to-github-actions.md

@@ -147,7 +147,7 @@ To help you understand how YAML syntax is used to create a workflow file, this s
   ```
 </td>
 <td>
-  Groups together all the steps that run in the <code>check-bats-version</code> job. Each line nested under this section is a separate action.
+  Groups together all the steps that run in the <code>check-bats-version</code> job. Each item nested under this section is a separate action or shell command.
 </td>
 </tr>
 <tr>