see https://github.com/rust-lang/crates.io/pulls?q=is%3Apr+is%3Aclosed+opengraph for the crates.io implementation and [their subcrate](https://github.com/rust-lang/crates.io/tree/main/crates/crates_io_og_image). I imagine it's an image to be generated for each crate. These would then be example [from this crates.io page](https://crates.io/crates/hashbrown) is [this image](https://static.crates.io/og-images/hashbrown.png). I imagine some details might be different. This needs `typst` locally installed on the docs.rs server.