Document log format configs in valkey.conf

Signed-off-by: azuredream <[email protected]>

valkey.conf

@@ -348,6 +348,19 @@ pidfile /var/run/valkey_6379.pid
 # nothing (nothing is logged)
 loglevel notice
 
+# Specifies the format used for logging Redis server messages.
+# This can be one of:
+# legacy (traditional Redis log format)
+# logfmt (Structured log format "logfmt")
+log-format legacy
+
+# log_timestamp_format - Specifies the timestamp format used in Redis logs.
+# This can be one of:
+# legacy       (traditional Redis timestamp format)
+# iso8601      (ISO 8601)
+# milliseconds (milliseconds since the epoch)
+log-timestamp-format legacy
+
 # Specify the log file name. Also the empty string can be used to force
 # the server to log on the standard output. Note that if you use standard
 # output for logging but daemonize, logs will be sent to /dev/null