Implement Unity GameObject pooling

[KurtGokhan]

When creating new elements, many new GameObjects will be created on Unity side. This is a problem especially since some components drop the framerate on initialization (like TextMeshPRO). Such components (or ideally all components) should be pooled and recycled.

This was requested in Discord. Here is a simple example of how to implement it.

[KurtGokhan]

Done in main branch. Will be released in next version.

[KurtGokhan]

Added pool property to all elements, accepting either boolean or string. This will group similar elements in a pool and recycle elements from that pool instead of creating/destroying them each time. This is enabled by default for text elements. Will observe how it works and may improve it in the next versions.