Restore preload all images option in popup

[sproclavism]

Is your feature request related to a problem? Please describe. Without this option, there is no way to load in all images on a specific page, without always preloading with the global setting.

Describe the solution you'd like It would be really nice if the previous preload option from the popup menu would be restored.

Describe alternatives you've considered If the proposed solution would take up too much space in the popup, another option would be to add a context-menu option to trigger the preloading.

Additional context Option removed in this change: #887

If the maintainer can give the ok, I'd be happy to implement the change and create a PR 🙂

(This is is a possible duplicate of #909, but I'm not sure since the explanation is not very clear.)