Small adjustment to the Guide to using https://kibana.siem.estc.dev/ …

…for local development (elastic#1104)

Just added a `xpack.lists.listItemIndex` setting which is also used by the `lists` plugin.

docs/common/running-the-security-app-on-any-branch-for-development-demos-and-testing/guide-to-using-kibana-siem-estc-dev-for-local-kibana-development.mdx

@@ -36,6 +36,7 @@ kibana.index: '.kibana-USERNAME'
 xpack.task_manager.index: '.kibana-task-manager-USERNAME'
 xpack.securitySolution.signalsIndex: '.siem-signals-USERNAME'
 xpack.lists.listIndex: '.lists-USERNAME'
+xpack.lists.listItemIndex: '.items-USERNAME'
 ```
 
 Replace `USERNAME` with your new username and `PASSWORD` with the password. Note that `USERNAME` is found several times in the text and needs to be replaced in each case.