Add a requestHandler setting to BaseAPI.

It mirrors `responseHandler` and it's useful for the same reason:
to be able to adapt the data sent to the LMS.

dist/scorm2004.min.js

@@ -512,6 +512,9 @@ var BaseAPI = /*#__PURE__*/function () {
           }
 
           return result;
+        },
+        requestHandler: function requestHandler(commitObject) {
+          return commitObject;
         }
       }
     });
@@ -1611,6 +1614,8 @@ var BaseAPI = /*#__PURE__*/function () {
           }
 
           try {
+            params = settings.requestHandler(params);
+
             if (params instanceof Array) {
               httpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
               httpReq.send(params.join('&'));