Update http_request_html.dart

emphasizing that response interception has still to be implemented for web

@@ -53,6 +53,19 @@ class HttpRequestImpl implements IClient {
       reader.onLoad.first.then((_) async {
         var bodyBytes = (reader.result as List<int>).toStream();
 
+        if(request.responseInterceptor != null) throw 'response interception not implemented for web yet!';
+
+        /*
+        TODO to be implemented like in http_request_io.dart
+        final interceptionResponse = await request.responseInterceptor?.call(request, T, reponse);
+
+        if (interceptionResponse != null) {
+          completer.complete(interceptionResponse);
+          return;
+        }
+
+        */
+
         final stringBody =
             await bodyBytesToString(bodyBytes, xhr.responseHeaders);