[DOCS] Add `has-passwd` parameter (#77594) (#79064)

Co-authored-by: Tim Vernum <tim@adjective.org>
Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com
Co-authored-by: ThiagoCruzBr <thiagocruz@gmail.com>

docs/reference/commands/keystore.asciidoc

@@ -14,6 +14,7 @@ bin/elasticsearch-keystore
 ( [add <settings>] [-f] [--stdin]
 | [add-file (<setting> <path>)+]
 | [create] [-p]
+| [has-passwd]
 | [list]
 | [passwd]
 | [remove <setting>]
@@ -68,6 +69,10 @@ password protected.
 
 `-h, --help`:: Returns all of the command parameters.
 
+`has-passwd`:: Returns a success message if the keystore exists and is
+password-protected. Otherwise, the command fails with exit code 1 and returns an
+error message.
+
 `list`:: Lists the settings in the keystore. If the keystore is password
 protected, you are prompted to enter the password.