allow fetching any resource under js folder via packager

Summary: This is a simple hook to allow native side to fetch any file under the js root folder via packager. Historically, only the `main.jsbundle` is fetched via the packager. This then allows fetching local file like a json file that lives under the same root js folder

Reviewed By: yungsters

Differential Revision: D4037730

fbshipit-source-id: a2d6eb5e30d148fee573d413fc4036d0189f4938

React/Base/RCTBundleURLProvider.h

@@ -32,6 +32,15 @@ extern const NSUInteger kRCTBundleURLProviderDefaultPort;
 - (NSURL *)jsBundleURLForBundleRoot:(NSString *)bundleRoot
                    fallbackResource:(NSString *)resourceName;
 
+/**
+ * Returns the resourceURL for a given bundle entrypoint and
+ * the fallback offline resource file if the packager is not running.
+ */
+- (NSURL *)resourceURLForResourceRoot:(NSString *)root
+                         resourceName:(NSString *)name
+                    resourceExtension:(NSString *)extension
+                        offlineBundle:(NSBundle *)offlineBundle;
+
 /**
  * Returns the URL of the packager server.
  */
@@ -58,4 +67,13 @@ extern const NSUInteger kRCTBundleURLProviderDefaultPort;
                           enableDev:(BOOL)enableDev
                  enableMinification:(BOOL)enableMinification;
 
+/**
+ * Given a hostname for the packager and a resource path (including "/"), return the URL to the resource.
+ * In general, please use the instance method to decide if the packager is running and fallback to the pre-packaged
+ * resource if it is not: -resourceURLForResourceRoot:resourceName:resourceExtension:offlineBundle:
+ */
++ (NSURL *)resourceURLForResourcePath:(NSString *)path
+                         packagerHost:(NSString *)packagerHost
+                                query:(NSString *)query;
+
 @end