Rename icon to notiticationIcon and add documentation

Author: manuquentin

README.md

@@ -53,6 +53,7 @@ const options = {
       channelId: 'com.company.my',
       channelName: 'Foreground service for my app',
       notificationTitle: 'My app is running on background',
+      notiticationIcon: 'Path to the resource icon of the notification',
     }, 
   }
 };
@@ -141,6 +142,7 @@ RNCallKeep.setForegroundServiceSettings({
     channelId: 'com.company.my',
     channelName: 'Foreground service for my app',
     notificationTitle: 'My app is running on background',
+    notiticationIcon: 'Path to the resource icon of the notification',
 });
 ```
 

android/src/main/java/io/wazo/callkeep/VoiceConnectionService.java

@@ -240,10 +240,10 @@ private void startForegroundService() {
             .setPriority(NotificationManager.IMPORTANCE_MIN)
             .setCategory(Notification.CATEGORY_SERVICE);
 
-        if (foregroundSettings.hasKey("icon")) {
+        if (foregroundSettings.hasKey("notificationIcon")) {
             Context context = this.getApplicationContext();
             Resources res = context.getResources();
-            String smallIcon = foregroundSettings.getString("icon");
+            String smallIcon = foregroundSettings.getString("notificationIcon");
             notificationBuilder.setSmallIcon(res.getIdentifier(smallIcon, "mipmap", context.getPackageName()));
         }