chore: implement track by carrier and number docs (#31)

* void label docs

* track by label id

* track by carrier code and tracking number

Author: j-r-j

docs/trackUsingCarrierCodeAndTrackingNumberExample.md

@@ -0,0 +1,57 @@
+Track Using Carrier Code and Tracking Number
+======================================
+[ShipEngine](www.shipengine.com) allows you to track a package for a given carrier and tracking number. Please see [our docs](https://www.shipengine.com/docs/tracking/) to learn more about tracking shipments.
+
+Input Parameters
+-------------------------------------
+
+The `trackUsingCarrierCodeAndTrackingNumber` method requires the carrier code and tracking number of the shipment being tracked.
+
+Output
+--------------------------------
+The `trackUsingCarrierCodeAndTrackingNumber` method returns tracking information associated with the shipment for the carrier code and tracking number.
+
+Example
+==============================
+```php
+use ShipEngine\ShipEngine;
+use ShipEngine\Message\ShipEngineException;
+
+function trackUsingCarrierCodeAndTrackingNumberDemoFunction() {
+  $client = new ShipEngine('API-Key');
+  try {
+    print_r($client->trackUsingCarrierCodeAndTrackingNumber('stamps_com', '9405511899223197428490'));
+  } catch (ShipEngineException $e) {
+    print_r($e -> getMessage());
+  }
+}
+
+trackUsingCarrierCodeAndTrackingNumberDemoFunction();
+```
+
+Example Output
+-----------------------------------------------------
+
+### Tracking Result
+```php
+Array
+(
+    [tracking_number] => 9405511899223197428490
+    [tracking_url] => https://tools.usps.com/go/TrackConfirmAction.action?tLabels=9405511899223197428490
+    [status_code] => NY
+    [carrier_code] => stamps_com
+    [carrier_id] => 1
+    [carrier_detail_code] =>
+    [status_description] => Not Yet In System
+    [carrier_status_code] => -2147219283
+    [carrier_status_description] => A status update is not yet available for this tracking number.  More information will become available when USPS receives the tracking information, or when the package is received by USPS.
+    [ship_date] =>
+    [estimated_delivery_date] =>
+    [actual_delivery_date] =>
+    [exception_description] =>
+    [events] => Array
+        (
+        )
+
+)
+```