Social media (OG) image previews

[NagariaHussain]

We need a way to attach OG image to individual wiki pages.

Or generating a automatic default preview image based on title / subtitle would be great.

Or letting the user write a template for generating an OG image would be even more magical. 🤩

[NagariaHussain]

Actually, the main feature request in this PR is generation of automatic OG images, so let it be open for now 😂