notify when modal dismissed (after animation if exists) (#736)

ios/RCCManagerModule.m

         [vc dismissViewControllerAnimated:![animationType isEqualToString:@"none"]
                                completion:^(){ resolve(nil); }];
     }
+    else
+    {
+      resolve(nil);
+    }
 }
 
 RCT_EXPORT_METHOD(

src/deprecated/controllers/index.js

       _validateDrawerProps(layout);
       RCCManager.showController(layout, animationType, passProps);
     },
-    dismissController: function(animationType = 'slide-down') {
-      RCCManager.dismissController(animationType);
+    dismissController: async function(animationType = 'slide-down') {
+      return await RCCManager.dismissController(animationType);
     },
     dismissAllControllers: function(animationType = 'slide-down') {
       RCCManager.dismissAllControllers(animationType);

src/deprecated/platformSpecificDeprecated.ios.js

   Modal.showController(controllerID, params.animationType);
 }
 
-function dismissModal(params) {
-  Modal.dismissController(params.animationType);
+async function dismissModal(params) {
+  return await Modal.dismissController(params.animationType);
 }
 
 function dismissAllModals(params) {