I feel like this should be implemented into core. It seems like a small enough detail where it would only take a few more lines of code and realistically, this feature is needed. Discord used this as well to expand links and it seems like a good thing to have for all installs.
The image could be the first image displayed in the original post, and if there isn't one, it could be set to the forum's logo (soon to be added to core).
The url would be the... well... Url.
The title would of coarse be the title of the post.
Description could be a getPlainContext() similar to the way the sticky extension gets it's description.
Fb app id? I assume that could be added to the Facebook auth extension.