[Main][Task] 28050373: Expose Offline Support SendNextBatch function (#2357)

* expose send next batch

* update

channels/offline-channel-js/src/OfflineChannel.ts

@@ -248,6 +248,11 @@ export class OfflineChannel extends BaseTelemetryPlugin implements IChannelContr
 
             };
 
+            _self.sendNextBatch = () => {
+                // TODO: add callback function
+                return _setSendNextTimer();
+            };
+
             _self._doTeardown = (unloadCtx?: IProcessTelemetryUnloadContext, unloadState?: ITelemetryUnloadState) => {
                 _self.onunloadFlush();
                 _offlineListener && runTargetUnload(_offlineListener, false);
@@ -740,4 +745,11 @@ export class OfflineChannel extends BaseTelemetryPlugin implements IChannelContr
     public onunloadFlush() {
         // @DynamicProtoStub -- DO NOT add any code as this will be removed during packaging
     }
+
+    /**
+     * Flush the next stored event batch
+     */
+    public sendNextBatch() {
+        // @DynamicProtoStub -- DO NOT add any code as this will be removed during packaging
+    }
 }