feat: add listTarget api (#1602)

* feat: add listTarget api
* test: write Platform API target list specs

lib/Api.js

@@ -277,6 +277,12 @@ class Api {
         });
     }
 
+    listTargets (options) {
+        return require('./check_reqs').check_android().then(() => {
+            return require('./run').runListDevices.call(this, options);
+        });
+    }
+
     /**
      * Cleans out the build artifacts from platform's directory, and also
      * cleans out the platform www directory if called without options specified.