Mark as read on hold-to-peek

### Is Your Feature Request Related to a Problem? When in compact mode, I don't usually care about loading the full res on meme posts, and is perfectly content with the near-instant but low quality peek. ### Feature Description In addition to `Mark Read after Viewing Media`, I'd like a `Mark Read after Peek` toggle. Note: I'd like for this to work for article peeks as well as media. ### Alternative Solutions Sometimes opening the full post (and letting the thumbnail show) then hitting back is much quicker than actually waiting on the full-res image to load. ### Additional Context Some shitposters really care about the quality of their images. I'd like to still be able to quickly enjoy their content, mark the posts as read, and never see them again on reload (with "Show Read Posts" turned off).