* Imoprove docs for callback shapes
* Improve docs for loader traits
* Use snake_case for feature `all_loaders`
* Make loaders publix
* Slightly better error message on image load failure
* Improve image loading error messages
* Use `bytes://` schema for included bytes loader
* Try user loaders first
* Move `image_loading_spinners` to `Visuals`
* Unify and simplify code
* Make the main text of `Button` optional
This largely makes ImageButton obsolete
* Fix docstrings
* Better docs
* typos
* Use the more explicit `egui_extras::install_image_loaders`
* Simplify `Image::paint_at` function
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