add documentation for use compound file setting (#7092)

* add documentation for use compound file setting

Signed-off-by: Samuel Herman <sherman8915@gmail.com>

* Update _install-and-configure/configuring-opensearch/index-settings.md

Co-authored-by: Andrew Ross <andrross@amazon.com>
Signed-off-by: samuel-oci <97131656+samuel-oci@users.noreply.github.com>

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Signed-off-by: Samuel Herman <sherman8915@gmail.com>
Signed-off-by: samuel-oci <97131656+samuel-oci@users.noreply.github.com>
Co-authored-by: Andrew Ross <andrross@amazon.com>

Author: sam-herman

_install-and-configure/configuring-opensearch/index-settings.md

@@ -125,6 +125,8 @@ For `zstd`, `zstd_no_dict`, `qat_lz4`, and `qat_deflate`, you can specify the co
 
 - `index.check_pending_flush.enabled` (Boolean): This setting controls the Apache Lucene `checkPendingFlushOnUpdate` index writer setting, which specifies whether an indexing thread should check for pending flushes on an update in order to flush indexing buffers to disk. Default is `true`.
 
+- `index.use_compound_file` (Boolean): This setting controls the Apache Lucene `useCompoundFile` index writer settings, which specifies whether newly written segment files will be packed into a compound file. Default is `true`.
+
 ### Updating a static index setting
 
 You can update a static index setting only on a closed index. The following example demonstrates updating the index codec setting.