Social media previews

Tracking issue for Kai to look into og:image tags on our pages. They don't seem to be working as expected re: gitbook docs and may need to follow up with their support forum.

No file, test, or entry point is named. Start by inspecting the pages' og:image tags and checking the GitBook documentation behavior, then consult the GitBook support forum if needed. Done means determining why the social previews are not working and recording the appropriate follow-up or fix.

Written by the indexing model from the issue text.