Simplify social images and add ability to set per-page images (#36804)

* Simplify social images and add ability to set per-page images

- Removes the homepage summary layout in favor of the larger image card (makes it more consistent with other pages)
- Reuses new thumbnails for Webpack, Parcel, and Vite guides to add their new social images

* Update default social card

* Change description to subtitle, add longer description to match homepage

* Remove social_image_path, use inline conditions for social images