fix: add "Point" objectType to TiledObject from Tiled 1.1 update

[ninjamuffin99]

In Tiled 1.1 there was a Point object type added.

https://doc.mapeditor.org/en/stable/manual/objects/#insert-point

The changes needed are relatively simple, we just want to set objectType so if we do something like
if (object.objectType == TiledObject.POINT) it's nice and conveniently there. It doesn't have any extra attributes that isn't already initialized

from my .tmx file

<object id="5" name="playerStart" x="1195.76" y="697.314">
   <point/>
</object>