add beginRefresh func

Author: 2534290808

MJRefresh.js

@@ -32,6 +32,9 @@ class MJRefresh extends Component {
     finishRefresh=()=>{
         this.dispatchCommand('finishRefresh');
     }
+    beginRefresh=()=>{
+        this.dispatchCommand('beginRefresh')
+    }
     dispatchCommand (commandName, params) {
         UIManager.dispatchViewManagerCommand(this.findNode(), UIManager.RCTMJRefreshView.Commands[commandName], params)
     }

ios/RCTMJRefreshHeader/RCTMJRefreshHeader/RCTMJRefreshViewManager.m

@@ -53,6 +53,17 @@ - (NSArray *)customDirectEventTypes
     }
   }];
 }
+RCT_EXPORT_METHOD(beginRefresh:(nonnull NSNumber *)reactTag)
+{
+    [self.bridge.uiManager addUIBlock:^(__unused RCTUIManager *uiManager, NSDictionary<NSNumber *, RCTMJRefreshHeader *> *viewRegistry) {
+        RCTMJRefreshHeader *view = viewRegistry[reactTag];
+        if (![view isKindOfClass:[RCTMJRefreshHeader class]]) {
+            RCTLogError(@"Invalid view returned from registry, expecting RCTBarrage, got: %@", view);
+        } else {
+            [view beginRefreshing];
+        }
+    }];
+}
 -(void)loadNewData
 {