Added a couple of delegate methods to the network delegate

Author: “Malcolm

platform/darwin/core/http_file_source.mm

@@ -292,11 +292,20 @@ BOOL isValidMapboxEndpoint(NSURL *url) {
 
         assert(session);
 
+        if ([networkManager.delegate respondsToSelector:@selector(willSendRequest:)]) {
+            req = [networkManager.delegate willSendRequest:req];
+        }
+        
         request->task = [session
             dataTaskWithRequest:req
               completionHandler:^(NSData* data, NSURLResponse* res, NSError* error) {
                 session = nil;
 
+                if ([networkManager.delegate respondsToSelector:@selector(didReceiveResponse:data:error:)]) {
+                    [networkManager.delegate didReceiveResponse:res data:data error:error];
+                }
+            
+            
                 if (error && [error code] == NSURLErrorCancelled) {
                     [MLNNativeNetworkManager.sharedManager cancelDownloadEventForResponse:res];
                     return;

platform/darwin/include/mbgl/interface/native_apple_interface.h

@@ -10,6 +10,10 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (NSURLSession *)sessionForNetworkManager:(MLNNativeNetworkManager *)networkManager;
 
+-(NSMutableURLRequest *)willSendRequest:(NSMutableURLRequest *)request;
+
+-(void)didReceiveResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *)error;
+
 @required
 
 - (NSURLSessionConfiguration *)sessionConfiguration;