constructor() {
        // never clear cached geometries
        this.geometries = [];

        this.clear();
    }
Here we create a CacheManager class object
 This will store geometries attributes arrays, textures and WebGL programs in arrays
 This helps speed up slow synchronous CPU operations such as WebGL shaders compilations, images decoding, etc.

 returns :
 @this: our CacheManager class object
*