Way to add own mipmaps

User requested for feature to add individual midmap levels for texture which is used in QtQuick3d scene:

"Ideally I would like to define the levels by some kind of array of image file URLs (so an array instead of a single URL for the Texture source property). For now I am using the automatic mipmap generation, but for precise control of the scene I am rendering I prefer making the mipmap textures myself."