增加内存警告插件 使用文档

uni_modules/uni-memorywarning/readme.md

-# wa-onMemoryWarning
-### 开发文档
-[UTS 语法](https://uniapp.dcloud.net.cn/tutorial/syntax-uts.html)
-[UTS 原生插件](https://uniapp.dcloud.net.cn/plugin/uts-plugin.html)
-[Hello UTS](https://gitcode.net/dcloud/hello-uts/-/tree/dev)
\ No newline at end of file
+## 使用说明
+
+### uni.onMemoryWarning(function listener)
+
+监听内存不足告警事件(目前仅Android)
+
+
+当 Android 向小程序进程发出内存警告时，触发该事件。
+
+触发该事件不意味应用被杀，大部分情况下仅仅是告警，开发者可在收到通知后回收一些不必要资源。
+
+返回值说明:
+
+```kotlin
+
+/**
+ * The device is beginning to run low on memory. Your app is running and not killable.
+ */
+int TRIM_MEMORY_RUNNING_MODERATE = 5;
+/**
+ * The device is running much lower on memory. Your app is running and not killable, but please release unused resources to improve system performance (which directly impacts your app's performance).
+ */
+int TRIM_MEMORY_RUNNING_LOW = 10;
+/**
+ * The device is running extremely low on memory. Your app is not yet considered a killable process, but the system will begin killing background processes if apps do not release resources, 
+ * so you should release non-critical resources now to prevent performance degradation.
+ */
+int TRIM_MEMORY_RUNNING_CRITICAL = 15;
+/**
+ * The device is beginning to run low on memory. Your app is running and not killable.
+ */
+int TRIM_MEMORY_UI_HIDDEN = 20;
+/**
+ * The system is running low on memory and your process is near the beginning of the LRU list. 
+ * Although your app process is not at a high risk of being killed, the system may already be killing processes in the LRU list, 
+ * so you should release resources that are easy to recover so your process will remain in the list and resume quickly when the user returns to your app.
+ */
+int TRIM_MEMORY_BACKGROUND = 40;
+/**
+ * The system is running low on memory and your process is near the middle of the LRU list. 
+ * If the system becomes further constrained for memory, 
+ * there's a chance your process will be killed.
+ */
+int TRIM_MEMORY_MODERATE = 60;
+/**
+ * The system is running low on memory and your process is one of the first to be killed if the system does not recover memory now. 
+ * You should release absolutely everything that's not critical to resuming your app state.
+ */
+int TRIM_MEMORY_COMPLETE = 80;
+
+```
+
+
+关于返回值的更多说明:[android官方文档](https://developer.android.com/reference/android/content/ComponentCallbacks2)
+
+### uni.offMemoryWarning(function listener)
+
+移除内存不足告警事件的监听函数(目前仅Android)
+
+onMemoryWarning 传入的监听函数。不传此参数则移除所有监听函数。
+