Add 'Update Search Index'

Update-Search-Index.md

@@ -0,0 +1,7 @@
+To update the search index use the tool `index_metadata`.
+
+Set the correct authentication variables.
+
+```
+python tools/index_metadata.py --hosts opensearch.eco.tsi-dev.otc-service.com:443 --target-environment public --index search_index_de --username <username> --password <password> --delete-index
+```