refactor: make async storage a peer dependency

`@segment/analytics-react-native` has an option to create custom persistor that matches `Persistor` type
from `@segment/sovran-react-native`. If it's possible, then let's mark
`@react-native-async-storage/async-storage` as optional peer dependency to not force users to download it when
custom persistor is used.

- `@react-native-async-storage/async-storage` is marked as optional peer dependency
- `@react-native-async-storage/async-storage` is optionally required (instead of being imported) in
`src/persistor/async-storage-persistor.ts`

Author: mateusz1913

package.json

@@ -157,11 +157,16 @@
     }
   },
   "peerDependencies": {
+    "@react-native-async-storage/async-storage": "*",
     "react": "*",
     "react-native": "*"
   },
+  "peerDependenciesMeta": {
+    "@react-native-async-storage/async-storage": {
+      "optional": true
+    }
+  },
   "dependencies": {
-    "@react-native-async-storage/async-storage": "^1.15.15",
     "ansi-regex": "5.0.1",
     "deepmerge": "^4.2.2",
     "shell-quote": "1.7.3"

src/persistor/async-storage-persistor.ts

@@ -1,13 +1,23 @@
-import AsyncStorage from '@react-native-async-storage/async-storage';
 import type { Persistor } from './persistor';
 
+let AsyncStorage: {
+  getItem: (key: string) => Promise<string | null>;
+  setItem: (key: string, value: string) => Promise<void>;
+} | null;
+
+try {
+  AsyncStorage = require('@react-native-async-storage/async-storage');
+} catch (error) {
+  AsyncStorage = null;
+}
+
 /**
  * Persistor implementation using AsyncStorage
  */
 export const AsyncStoragePersistor: Persistor = {
   get: async <T>(key: string): Promise<T | undefined> => {
     try {
-      const persistedStateJSON = await AsyncStorage.getItem(key);
+      const persistedStateJSON = await AsyncStorage?.getItem?.(key);
       if (persistedStateJSON !== null && persistedStateJSON !== undefined) {
         return JSON.parse(persistedStateJSON);
       }
@@ -20,7 +30,7 @@ export const AsyncStoragePersistor: Persistor = {
 
   set: async <T>(key: string, state: T): Promise<void> => {
     try {
-      await AsyncStorage.setItem(key, JSON.stringify(state));
+      await AsyncStorage?.setItem?.(key, JSON.stringify(state));
     } catch (e) {
       console.error(e);
     }