Add link error hint

lib/index.js

@@ -1,7 +1,11 @@
 import getHost, { tryBackupDomains } from './getHost';
 import { NativeAppEventEmitter, NativeModules } from 'react-native';
 
-const Pushy = NativeModules.Pushy || {};
+let Pushy = NativeModules.Pushy;
+
+if (!Pushy) {
+  throw new Error('react-native-update模块无法加载，请对照安装文档检查配置。');
+}
 
 export const downloadRootDir = Pushy.downloadRootDir;
 export const packageVersion = Pushy.packageVersion;
@@ -111,6 +115,11 @@ export function markSuccess() {
   Pushy.markSuccess();
 }
 
+// function report(action) {
+//   // ${project}.${host}/logstores/${logstore}/track?APIVersion=0.6.0&key1=val1
+//   fetch(`${logUrl}&action=${action}`);
+// }
+
 NativeAppEventEmitter.addListener('RCTPushyDownloadProgress', params => {});
 
 NativeAppEventEmitter.addListener('RCTPushyUnzipProgress', params => {});