Update README.md

Author: IntoTheDev

README.md

@@ -17,7 +17,7 @@ or
 Open the manifest.json file of your Unity project.
 Add ```"com.intothedev.objectpooling": "https://github.com/IntoTheDev/Object-Pooling-for-Unity.git"```
 
-### Manual Installation
+### Manual Installation (Version can be outdated)
 Download latest package from the Release section
 Import ObjectPooling.unitypackage to your Unity Project