Returns a Texture from the Texture Manager that matches the given key.
If the key is
undefined it will return the
If the key is an instance of a Texture, it will return the key directly.
Finally. if the key is given, but not found and not a Texture instance, it will return the
|key||string | Phaser.Textures.Texture||
The unique string-based key of the Texture, or a Texture instance.
The Texture that was created.