NH-65373: add SW_APM_TRANSACTION_NAME to configuration.md

Author: xuan-cao-swi

CONFIGURATION.md

@@ -162,6 +162,7 @@ Environment Variable | Config File Key | Description | Default
 `SW_APM_TAG_SQL` | `:tag_sql` | Enable/disable injecting trace context into supported SQL statements. Set to boolean true or (or string `true` in env var) to enable, see [Tag Query with Trace Context](#tag-query-with-trace-context) for details.| false
 `SW_APM_TRIGGER_TRACING_MODE` | `:trigger_tracing_mode` | Enable/disable trigger tracing for the service.  Setting to `disabled` may impact DEM visibility into the service. | `enabled`
 `SW_APM_TRUSTEDPATH` | N/A | The library uses the host system's default trusted CA certificates to verify the TLS connection to the collector. To override the default, define the trusted certificate path configuration option with an absolute path to a specific trusted certificate file in PEM format. | None
+`SW_APM_TRANSACTION_NAME` | N/A | Customize the transaction name of trace. _Predecessor order_: custom SDK > `SW_APM_TRANSACTION_NAME` > automatic naming | None
 N/A | `:log_args` | Enable/disable the collection of URL query parameters, set to boolean false to disable. | true
 N/A | `:log_traceId` | Configure the insertion of trace context into application logs, setting `:traced` would include the available context fields such as trace_id, span_id into log messages. | `:never`
 N/A | `:tracing_mode` | Enable/disable the tracing mode for this service, setting `:disabled` would suppress all trace spans and metrics. | `:enabled`