Add notifications permission to manifest

Author: aurimasc

com.unity.mobile.notifications/Editor/AndroidNotificationPostProcessor.cs

@@ -82,6 +82,8 @@ private void InjectAndroidManifest(string projectPath)
                 AppendAndroidPermissionField(manifestPath, manifestDoc, "android.permission.RECEIVE_BOOT_COMPLETED");
             }
 
+            AppendAndroidPermissionField(manifestPath, manifestDoc, "android.permission.POST_NOTIFICATIONS");
+
             manifestDoc.Save(manifestPath);
         }