[Feature Request] Generate all thumbnails button in settings

[theontho]

Is your feature request related to a problem? Please describe. Waiting for thumbnail generation adds friction. Also if you resize your default thumbnail size, it would be useful to also regenerate them

Describe the solution you'd like A button in settings to generate all thumbnails and keep them cached, might as well do it while the program is idle, you go to the bathroom, etc. Helps with initial adoption experience

Describe alternatives you've considered tediously scrolling through my images