The `GdkTextureDownloader` is used to download the contents of a [class@Gdk.
Texture].
It is intended to be created as a short-term object for a single download, but can be used for multiple downloads of different textures
or with different settings.
`GdkTextureDownloader` can be used to convert data between different formats. Create a `GdkTexture` for the existing format and then
download it in a different format.