chore: Adds docs for Android permissions (#202)

* Adds docs for Android permissions

* Corrected typo's and imporovements

* Include CLI as a case explicitly

* Remove unexpected pasted lines

README.md

@@ -57,14 +57,21 @@ import CameraRoll from "@react-native-community/cameraroll";
 
 ### Permissions
 
+**iOS**
+
 The user's permission is required in order to access the Camera Roll on devices running iOS 10 or later. Add the `NSPhotoLibraryUsageDescription` key in your `Info.plist` with a string that describes how your app will use this data. This key will appear as `Privacy - Photo Library Usage Description` in Xcode.
 
 If you are targeting devices running iOS 11 or later, you will also need to add the `NSPhotoLibraryAddUsageDescription` key in your `Info.plist`. Use this key to define a string that describes how your app will use this data. By adding this key to your `Info.plist`, you will be able to request write-only access permission from the user. If you try to save to the camera roll without this permission, your app will exit.
 
-On Android permission is required to read the external storage. Add below line to your manifest to request this permission on app install.
-On Android permission is required to write in the external storage when saving to camera roll. Add below line to your manifest to request this permission on app install.
+**Android**
 
-```
+Permission is required to read and write to the external storage.
+
+On Expo, follow the guide [here](https://docs.expo.io/versions/latest/sdk/permissions/) for requesting the permission.
+
+On react-native-cli or ejected apps, adding the following lines will add the capability for the app to request the permission. Find more info on Android Permissions [here](https://reactnative.dev/docs/permissionsandroid).
+
+```xml
 <manifest>
 ...
 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
@@ -73,6 +80,33 @@ On Android permission is required to write in the external storage when saving t
 <application>
 ```
 
+Then you have to explicitly ask for the permission
+
+```javascript
+import { PermissionsAndroid, Platform } from "react-native";
+import CameraRoll from "@react-native-community/cameraroll";
+
+async function hasAndroidPermission() {
+  const permission = PermissionsAndroid.PERMISSIONS.WRITE_EXTERNAL_STORAGE;
+
+  const hasPermission = await PermissionsAndroid.check(permission);
+  if (hasPermission) {
+    return true;
+  }
+
+  const status = await PermissionsAndroid.request(permission);
+  return status === 'granted';
+}
+
+async function savePicture() {
+  if (Platform.OS === "android" && !(await hasAndroidPermission())) {
+    return;
+  }
+
+  CameraRoll.saveToCameraRoll(tag, [type]);
+};
+```
+
 ### Methods
 
 * [`save`](#save)