doc(android): add quirks for WRITE_EXTERNAL_STORAGE permission (#386)

README.md

@@ -56,6 +56,22 @@ cordova plugin add cordova-plugin-media
 - iOS
 - Browser
 
+### Android Quirks
+
+#### SDK Target Less Than 29
+
+From the official [Storage updates in Android 11](https://developer.android.com/about/versions/11/privacy/storage) documentation, the [`WRITE_EXTERNAL_STORAGE`](https://developer.android.com/reference/android/Manifest.permission#WRITE_EXTERNAL_STORAGE) permission is no longer operational and does not provide access.
+
+> If this permission is not allowlisted for an app that targets an API level before [`Build.VERSION_CODES.Q`](https://developer.android.com/reference/android/os/Build.VERSION_CODES#Q) (SDK 29) this permission cannot be granted to apps.
+
+If you need to add this permission, please add the following to your `config.xml`.
+
+```xml
+<config-file target="AndroidManifest.xml" parent="/*" xmlns:android="http://schemas.android.com/apk/res/android">
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="28" />
+</config-file>
+```
+
 ## Media
 
 ```js