[Feature] Use <picture> element for image fallback

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature Currently the web client requests a specific image version (original, fullsize, preview) based on the context and user/admin settings. In case of an unsupported mime type, the browser will render a fullsize image (if enabled) or a preview. Would you consider changing this logic to always use the fullsize and preview urls, along the original, as fallbacks in a <picture> [element]( Modifying the first example from MDN, the code could look like this: All <source> elements can be included or omitted to support the current logic: • Respecting the alwaysLoadOriginal user setting. • Showing the original when zooming in. • Fullsize generation admin toggle. This would take care of fallbacks, without manually checking compatibility for a specific mime type. It could also be potentially used to serve different i…